Altium import, nets, canonical pins, component kinds, set/$var, scrollback, source modal.

Major additions, all wired end-to-end with doctest coverage:

- Altium netlist importer (`imports/import_altium.{hpp,cpp}`): two-pass
  parser for `[ ]` parts and `( )` signals; `System::Load` no longer has
  the IMPORT_ALTIUM hole.
- `duplicate <src> <dst>` deep-copies a module (signals, parts, pins,
  rewired signals); connections excluded by design.
- Nets (`system/nets.{hpp,cpp}`): BFS over `Connection::pin_map` to
  return the transitive (Module, Signal) closure. `verify` extended with
  a second pass flagging Power↔GndShield inconsistencies in bridged
  nets; new `net <module> <signal>` command for inspection.
- Canonical pin names (`system/pin_name.{hpp,cpp}`): zero-padded digit
  suffix lets A1 ↔ A001 pair via `IdentityTransform` and
  `CheckIdentityCompatible` without losing the imported notation.
- Component classification (`system/component_kind.{hpp,cpp}`):
  `Part::kind` inferred at construction from the reference-designator
  prefix (longest-match: LED/TP/SW/FB/MK/MP/MH/HS/RA/RN/RP/RV first,
  then R/C/L/F/D/Q/U/J/P/Y/X/S).
- Identity wiring tolerance: `CheckIdentityCompatible` accepts the
  subset case (typical when one importer drops NC pins, e.g. Altium)
  and surfaces orphans as an info string. `FillIdentityNCs`
  materialises orphan canonical positions as NC pins on the missing
  side at connect time.
- Connector layout preparation: `pin_layout(kind)` and
  `FillPartFromLayout(part, kind)` stubs in `pin_role`, called from
  `set-type`. Empty today; populate alongside `vpx_3u_role`.
- TUI scrollback: PageUp/PageDown step 10 lines, Home/End jump to
  ends; `Print()` snaps back to the tail.
- `set <name> <value>` declares session variables; `$name` / `${name}`
  expanded inside `Finalize` between canonical-form recording and the
  action call — history and script-save preserve `$var` references.
- Long `source` scripts now show a centred "Computing…" modal with a
  N/M progress counter. Driven by a ticker thread that posts one
  paced `Event::Special` per processed line, ack'd by the main thread,
  so heavy lines don't backlog ticks and freeze the counter.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

CLAUDE.md

@@ -23,15 +23,25 @@ src/
   system/                -- domain model
     syselmts.hpp           SystemElement + SystemElementContainer<T> (templated, get/merge/iterate)
     modules.{hpp,cpp}      Module, Modules
-    parts.{hpp,cpp}        Part, Parts
+    parts.{hpp,cpp}        Part (carries `kind` + `connector_type`), Parts
     pins.{hpp,cpp}         Pin, Pins
     signals.{hpp,cpp}      Signal, Signals
+    signal_type.hpp        SignalType + helpers
+    component_kind.{hpp,cpp} ComponentKind enum + infer_component_kind(name)
+    pin_name.{hpp,cpp}     canonical_pin_name(s) — zero-pad digit suffix to 3
     connect.{hpp,cpp}      Connection, Connections
-    transform.{hpp,cpp}    transforms applied to the model
+    transform.{hpp,cpp}    Transform / IdentityTransform / TransformRegistry +
+                           CheckIdentityCompatible + FillIdentityNCs
+    pin_role.{hpp,cpp}     pin_role(kind, name), pin_layout(kind),
+                           FillPartFromLayout(part, kind)
+    nets.{hpp,cpp}         find_net / compute_all_nets / net_type_consistent
+    persist.{hpp,cpp}      save / restore (tab-delimited)
     system.{hpp,cpp}       System: owns Modules + Connections, exposes Load()
   imports/               -- adapters that populate the domain
     import_base.hpp        ImportBase interface
-    import_mentor.{hpp,cpp} Mentor Graphics netlist parser (done)
+    import_mentor.{hpp,cpp} Mentor Graphics netlist parser
+    import_altium.{hpp,cpp} Altium netlist parser (`[ ]` parts, `( )` signals)
+    import_ods.{hpp,cpp}   ODS spreadsheet pinout (libzip + pugixml)
   tui/                   -- FTXUI shell, split by responsibility
     tui.{hpp,cpp}          Class Tui (state + Run() orchestrator + screen-mode event dispatcher)
     tui_helpers.{hpp,cpp}  Free helpers: ToLower, NaturalLess, LongestCommonPrefix
@@ -71,7 +81,11 @@ doc/classes.puml         -- PlantUML class diagram
 - Multi-step prompts work via a `std::deque<Prompt>` queue. `Submit()` pops them one by one before falling back to dispatch. Adding a new command = one entry in `RegisterCommands()`; the prompt-flow and inline-flow are both handled automatically.
 - Tab completion: at the top-level prompt (no `pending`), completes built-in command names. Inside a prompt with `path_completion = true` (e.g. the `filename` step of `load`), completes file paths via `std::filesystem::directory_iterator` (handles `~/`, dirs get a trailing `/`). Logic: 1 match → replace; multiple with progress on the longest common prefix → extend; multiple stuck at LCP → list candidates in the visualisation area.
 
-Built-in commands: `new`, `load`, `save`, `restore`, `source`, `script-save`, `connect`, `set-type`, `search`, `explore`, `clear`, `help`, `quit`/`exit`. `Esc` cancels an in-progress multi-step prompt.
+Built-in commands: `new`, `set`, `load`, `duplicate`, `save`, `restore`, `source`, `script-save`, `connect`, `set-type`, `set-signal-type`, `search`, `explore`, `verify`, `net`, `clear`, `help`, `quit`/`exit`. `Esc` cancels an in-progress multi-step prompt.
+
+`set <name> <value>` declares a session-scoped variable. Subsequent commands expand `$name` and `${name}` in their args (substitution happens in `Finalize` between canonical-form recording and `spec.action(args)` — so `history` and `script-save` keep the **unexpanded** form, while the action sees resolved values). Unknown variables are left literal. `vars` is reset by `new`. Validation: `[A-Za-z_][A-Za-z0-9_]*`.
+
+`duplicate <source> <newname>` deep-copies a module: signals (with type overrides), parts (with `connector_type` and `kind`), pins (with `expected_signal_type`), and rewires each pin to the equivalent same-named signal in the new module. Connections are NOT copied (they're cross-module topology).
 
 `script-save <file>` writes a replay-ready script of every command issued since the last `new` (the `recorded` buffer is cleared inside the `new` action). The buffer is appended to inside `Finalize()` after the action runs, with a denylist of commands that aren't useful in a replay: `clear`, `help`, `quit`, `exit`, `source`, `script-save`. Note the `source` exclusion: when a script is sourced, the *individual lines inside* the script are recorded (because each goes through `Finalize`), so the saved script reproduces the same end state without the indirection.
 
@@ -85,15 +99,27 @@ Pending prompts (from incomplete inline commands) are NOT considered interactive
 
 **Signals** carry a `type` (`SignalType::Power | GndShield | Other`) auto-inferred from the name in `Signal::Signal` via `infer_signal_type` (heuristic: GND/GROUND/SHIELD/CHASSIS → GndShield; PWR/VCC/VDD/VEE/VSS/VBAT/VS_/VS3_*/+/- prefixes → Power; else Other). Override with `set-signal-type <module> <signal> <power|gnd|other>`. The explore screen shows the type in the signal detail header.
 
-**Pin role expectations**: every Pin carries an `expected_signal_type` populated by `set-type` from a per-(connector_type, pin_name) lookup (`src/system/pin_role.{hpp,cpp}`). The framework is wired end-to-end; the actual VPX 3U lookup table is currently a stub returning Other for all positions — fill in `vpx_3u_role(col, row, idx)` with the real VITA 46 layout when needed. The `verify` command walks all typed parts and reports pins whose connected signal's type doesn't match the expectation.
+**Pin role expectations**: every Pin carries an `expected_signal_type` populated by `set-type` from a per-(connector_type, pin_name) lookup (`src/system/pin_role.{hpp,cpp}`). The framework is wired end-to-end; the actual VPX 3U lookup table is currently a stub returning Other for all positions — fill in `vpx_3u_role(col, row, idx)` with the real VITA 46 layout when needed.
+
+**Connector pin layout (preparation)**: `pin_layout(connector_type)` returns the canonical full pin-name list for a known connector kind, and `FillPartFromLayout(part, kind)` materialises NC pins for any layout position absent from the imported netlist. `set-type` calls it after setting `connector_type` (no-op today since `pin_layout` is a stub returning `{}` for everything — populate alongside `vpx_3u_role`). End-to-end chain in place: `set-type → FillPartFromLayout → pin_role`.
+
+**`verify` (two passes)**: walks all typed pins and reports local mismatches between `expected_signal_type` and the actual signal type, AND walks all bridged nets reporting Power↔GndShield inconsistencies. `net <module> <signal>` prints the BFS-reached `(module, signal)` set with types and an `[INCONSISTENT]` flag.
+
+**Component classification**: every `Part` carries a `ComponentKind kind` (`Passive | Semiconductor | IntegratedCircuit | Connector | TestPoint | Switch | Crystal | Mechanical | Other`) inferred at construction by `infer_component_kind(name)` from the leading reference-designator letter(s) (longest-match: `LED/TP/SW/FB/MK/MP/MH/HS/RA/RN/RP/RV` first, then single-letter R/C/L/F/D/Q/U/J/P/Y/X/S). Recomputed on `restore` (no persistence tag). Not yet exposed in TUI commands — branchpoints will be `search` filter, `set-type` guard, and `explore` header.
 
 `SignalType` lives in its own header `src/system/signal_type.hpp` (extracted from signals to avoid a pins↔signals include cycle).
 
 **Pins** are either NC (`signal() == nullptr`) or connected to exactly one signal. The ODS importer creates a Pin for every row that has a non-empty pin name, even when the signal column is empty or `"NC"` — the pin stays in the Part as NC. `restore` replaces `Tui::sys` entirely (`unique_ptr::reset`). Names are stored as-is — must not contain TAB or newline (true for the EE netlists we ingest). Format is versioned by the `# essim system snapshot v1` header for future compatibility.
 
-**Connector types & transforms**: every `Part` carries a `connector_type` string (default `""`, set via the `set-type` command — inline `set-type m p kind` or bare which opens a TUI screen with module menu, part filter+menu, type input, list of types already in use, and an Apply button). When `connect` validates a pair, it consults `TransformRegistry::lookup(p1->connector_type, p2->connector_type)` (defined in `src/system/transform.{hpp,cpp}`) — both directions of the pair are tried. If neither is registered, an `IdentityTransform` fallback wires each pin of A to the same-name pin of B (when present). The resulting `(Pin*, Pin*)` list and the transform's name are stored on the `Connection` (`pin_map`, `transform_name`). To register a real transform: define a `Transform` subclass in `transform.cpp` and call `TransformRegistry::get().add("kindA", "kindB", new MyTransform())` at init — there's no startup hook for this yet, so a small `RegisterBuiltinTransforms()` helper is the natural place to add when more types appear.
+**Connector types & transforms**: every `Part` carries a `connector_type` string (default `""`, set via the `set-type` command — inline `set-type m p kind` or bare which opens a TUI screen with module menu, part filter+menu, type input, list of types already in use, and an Apply button). When `connect` validates a pair, it consults `TransformRegistry::lookup(p1->connector_type, p2->connector_type)` (defined in `src/system/transform.{hpp,cpp}`) — both directions of the pair are tried. If neither is registered, an `IdentityTransform` fallback wires each pin of A to the canonical-equivalent pin of B (when present). The resulting `(Pin*, Pin*)` list and the transform's name are stored on the `Connection` (`pin_map`, `transform_name`). To register a real transform: define a `Transform` subclass in `transform.cpp` and call `TransformRegistry::get().add("kindA", "kindB", new MyTransform())` at init — there's no startup hook for this yet, so a small `RegisterBuiltinTransforms()` helper is the natural place to add when more types appear.
 
-`screen_idx` mapping: 0 = main TUI, 1 = search, 2 = connect, 3 = set-type. Adding a new screen mode is the same recipe each time: state members, `Container::Vertical` of focusable components, a `Renderer` lambda that recomputes derived state per frame (e.g. filtered part lists), an entry in `Container::Tab`, and Tab/Esc handling in the outer `CatchEvent`.
+**Identity wiring uses canonical names**: `IdentityTransform::apply` builds `unordered_map<canonical, Pin*>` for side B and looks up each side-A pin by its canonical form. So `A1` (one card) auto-pairs with `A001` (the other) thanks to `canonical_pin_name` (`pre + zero-padded(3) digit suffix`; mixed/non-numeric returns the original). Same canonicalisation in `CheckIdentityCompatible`. **`pin_role` doesn't need canonicalisation** because `parse_pin` extracts `(col, row)` via `stoi` which already strips leading zeros.
+
+**Subset wiring + NC backfill**: `CheckIdentityCompatible(a, b, info=&s)` accepts the case where one side's canonical pin set is a subset of the other's — typical when one importer drops NC pins (Altium) and the other doesn't (Mentor). It populates `info` with a non-fatal "N pin(s) only on '<part>'" message. Bidirectional mismatch (both sides have orphans) is still refused. After acceptance, `connect` calls `FillIdentityNCs(p1, p2)` which materialises the orphan canonical positions on the missing side as NC pins (`new Pin(other_side_name)`) — so `Connection::pin_map.size()` matches the larger side's count. Idempotent.
+
+`screen_idx` mapping: 0 = main TUI, 1 = search, 2 = connect, 3 = set-type, 4 = explore. Adding a new screen mode is the same recipe each time: state members, `Container::Vertical` of focusable components, a `Renderer` lambda that recomputes derived state per frame (e.g. filtered part lists), an entry in `Container::Tab`, and Tab/Esc handling in the outer `CatchEvent`.
+
+**Main-screen scrollback**: the visualisation area lets you scroll through past output. State is `Tui::scroll_offset` (0 = follow tail). Keys (default branch of the outer `CatchEvent` in `Run()`): `PageUp` / `PageDown` step 10 lines, `Home` jumps to top, `End` returns to tail. `Print()` resets `scroll_offset = 0` so any new output snaps the view back to the tail (otherwise late errors would be hidden). Render: instead of `focusPositionRelative(0, 1)` always anchoring to the bottom, the screen places `| focus` on `output[size - 1 - scroll_offset]` and shows a `[scroll: -N / PgUp PgDn Home End]` indicator next to the prompt when offset > 0. `vscroll_indicator | yframe` for the FTXUI-side scroll bar.
 
 `connect` is dual-mode (`prompt_for_missing = false`):
 - Inline: `connect m1 p1 m2 p2`. Each part argument is resolved as exact name first, then case-insensitive substring; ambiguous → lists candidates and aborts.
@@ -119,7 +145,8 @@ Each successful submission appends a single line to the file (so a crash doesn't
 
 ## Gotchas
 
-- `System::Load` for `IMPORT_ALTIUM`: the corresponding constructor line is still commented out, so `imp` stays uninitialised → UB on `imp->parse(...)`. `IMPORT_MENTOR` and `IMPORT_ODS` are wired. Wrap calls in `try/catch` (the TUI does).
+- All three importers (`IMPORT_MENTOR`, `IMPORT_ALTIUM`, `IMPORT_ODS`) are wired in `System::Load`. Wrap calls in `try/catch` (the TUI does).
+- **Altium importer drops NC pins entirely**: the source format only enumerates pins inside `(signal …)` blocks, so positions not connected to any signal on this card never become `Pin`s. Mentor (via `Explicit Pin:`) and ODS (one row per pin) materialise NC. This is the asymmetry that motivates `FillIdentityNCs` at `connect` time and (eventually) `FillPartFromLayout` at `set-type` time.
 - ODS importer: each spreadsheet sheet becomes a `Part` (sheet name = part name). Rows are pin/signal pairs; the **first non-empty row of each sheet is dropped as a header** (no validation of header content). Empty cells skip the row; `"NC"` keeps the pin in the part but doesn't connect it to a signal. Pins or parts whose name collides (rare in well-formed sheets) are silently dropped.
 - `System::Load` throws `std::runtime_error("Unknown import type")` for any value outside the three enum cases.
 - `Modules`/`Parts`/etc. have no const-correct iteration on the `*` accessor; iterators on `SystemElementContainer<T>` are available but `begin()`/`end()` are non-const-safe in some places.