User-facing docs: --commands-md flag, doc/user/ tree, anonymised script.

- `essim --commands-md [file]` instantiates the Tui, calls
  `Tui::DumpCommandsMd(ostream&)` which iterates the live registry and
  emits Markdown grouped by interactive/other, then exits. Single
  source of truth: a new `CommandSpec` field surfaces automatically.
- CMake `doc` target now `DEPENDS essim` and chains:
    doxygen → gen_api_md.py → doc/api/
    essim --commands-md      → doc/user/commands.md
- `doc/user/` adds:
    - index.md (hand-written) — first session, interactive-screen
      conventions, save/restore/replay overview.
    - scripting.md (hand-written) — `set`/`$var` expansion semantics,
      `source` event-paced execution, script-save denylist, worked
      example pointing at test/system.essim.
    - commands.md (auto-generated, regenerated by the `doc` target).
- Top-level README refocused on quick start; pointers to the new
  doc tree (user/, api/, DESIGN.md) instead of an inline command table.
- doc/README.md and DESIGN.md document the two-pipeline doc workflow.
- `test/system.essim` and user docs anonymised: bkp → backplane,
  vdn1/2/3 → payload1/2/3, cb3p → payload4, bpb/cob/ssu →
  peripheral1/2/3; netlist file names + variable names + paths all
  replaced with generic equivalents.

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

doc/user/commands.md

@@ -0,0 +1,242 @@
+# essim — command reference
+
+Auto-generated from the live command registry. Regenerate with
+`cmake --build build --target doc` after adding or changing
+commands; the binary itself is the single source of truth.
+
+Keys global to the shell: `Esc` cancels a multi-step prompt or
+leaves an interactive screen; `Tab` completes commands/paths
+(top-level prompt) or cycles focus inside an interactive
+screen; `PageUp` / `PageDown` scroll output by 10 lines,
+`Home` / `End` jump to top / bottom; ↑ / ↓ walk command
+history.
+
+## Interactive commands
+
+### `connect`  *(interactive)*
+
+connect a part across two modules (interactive screen if no args)
+
+**Arguments**
+
+1. `module1`
+2. `part1 (name or pattern)`
+3. `module2`
+4. `part2 (name or pattern)`
+
+**Notes**
+
+- bare form opens an interactive screen; inline form (all args) is scriptable
+
+---
+### `explore`  *(interactive)*
+
+browse modules → parts/signals/connections → details (interactive)
+
+**No arguments.**
+**Notes**
+
+- bare form opens an interactive screen; inline form (all args) is scriptable
+- not recorded by `script-save` and rejected by `source`
+
+---
+### `net`  *(interactive)*
+
+show all signals reachable from <module>/<signal> through connections (interactive screen if no args)
+
+**Arguments**
+
+1. `module`
+2. `signal name`
+
+**Notes**
+
+- bare form opens an interactive screen; inline form (all args) is scriptable
+
+---
+### `search`  *(interactive)*
+
+list parts/signals matching a pattern (interactive screen if no args)
+
+**Arguments**
+
+1. `module`
+2. `kind [parts|signals]`
+3. `pattern`
+
+**Notes**
+
+- bare form opens an interactive screen; inline form (all args) is scriptable
+
+---
+### `set-type`  *(interactive)*
+
+tag a part's connector type for transform lookup
+
+**Arguments**
+
+1. `module`
+2. `part (name or pattern)`
+3. `connector type (free string, e.g. vpx-bp, vpx-payload)`
+
+**Notes**
+
+- bare form opens an interactive screen; inline form (all args) is scriptable
+
+---
+
+## Other commands
+
+### `clear`
+
+clear the visualization area
+
+**No arguments.**
+---
+### `duplicate`
+
+clone a module under a new name (parts, pins, signals; no connections)
+
+**Arguments**
+
+1. `source module`
+2. `new module name`
+
+**Notes**
+
+- missing args trigger one prompt each
+
+---
+### `exit`
+
+leave essim (alias of quit)
+
+**No arguments.**
+---
+### `help`
+
+show command help (optionally for a specific command)
+
+**Arguments**
+
+1. `command name (optional)`  *(Tab → command completion)*
+
+**Notes**
+
+- no per-arg prompt: pass all args inline (or run bare for an empty-args path)
+
+---
+### `load`
+
+load a module from a netlist / pinout file (mentor, altium, ods)
+
+**Arguments**
+
+1. `module name`
+2. `filename`  *(Tab → path completion)*
+3. `import type [mentor|altium|ods]`
+
+**Notes**
+
+- missing args trigger one prompt each
+
+---
+### `new`
+
+create a new (empty) system; resets the script-save buffer and $vars
+
+**No arguments.**
+---
+### `quit`
+
+leave essim
+
+**No arguments.**
+---
+### `restore`
+
+replace the current system with a saved snapshot
+
+**Arguments**
+
+1. `filename`  *(Tab → path completion)*
+
+**Notes**
+
+- missing args trigger one prompt each
+
+---
+### `save`
+
+write the current system snapshot to a file
+
+**Arguments**
+
+1. `filename`  *(Tab → path completion)*
+
+**Notes**
+
+- missing args trigger one prompt each
+
+---
+### `script-save`
+
+write commands run since last 'new' as a replay-ready script
+
+**Arguments**
+
+1. `filename`  *(Tab → path completion)*
+
+**Notes**
+
+- missing args trigger one prompt each
+
+---
+### `set`
+
+define a $variable for substitution in subsequent commands (no args = list defined vars)
+
+**Arguments**
+
+1. `name`
+2. `value`
+
+**Notes**
+
+- no per-arg prompt: pass all args inline (or run bare for an empty-args path)
+
+---
+### `set-signal-type`
+
+override the auto-detected signal type (power | gnd | other)
+
+**Arguments**
+
+1. `module`
+2. `signal name`
+3. `type [power|gnd|other]`
+
+**Notes**
+
+- missing args trigger one prompt each
+
+---
+### `source`
+
+execute a file of commands line by line (interactive cmds rejected)
+
+**Arguments**
+
+1. `filename`  *(Tab → path completion)*
+
+**Notes**
+
+- missing args trigger one prompt each
+
+---
+### `verify`
+
+check pin roles locally and signal-type consistency across bridged nets
+
+**No arguments.**
+---