Export command (CSV + ODS), file dialog, error modal, path persistence.

New user-facing features:
- `export connections <file>` writes a tabular dump of every wire pair:
  connection, transform, left/right module/part/pin/signal/type/suspect,
  mixed-types flag. Dispatch on extension: `.csv` (flat file) or `.ods`
  (one sheet per connection). Any other extension shows an error and
  writes nothing.
- Bare `export` (or dashboard `[x]`, or palette `export`) opens an
  interactive file-picker dialog with a CSV/ODS toggle at the top.
  Picking a filter rewrites the filename's extension. Last-used
  directory and filename are remembered per-call-site.
- Two new CLI flags on the binary: `--source FILE` to run a script at
  boot, `--restore FILE` to restore a snapshot at boot. Combinable.

Reusable infrastructure:
- `OdsWriter` (`src/imports/ods_writer.{hpp,cpp}`): minimal .ods writer
  using libzip + pugixml (already in the build for the importer).
  Multi-sheet workbook of string cells. ~180 lines, no new dep.
- Generic file-picker dialog (`screen_filedialog.cpp`): one Modal
  reused for any "pick a path" interaction via
  `OpenFileDialog(title, persist_key, default_filename, filters, cb)`.
  Validates the picked extension against the filter whitelist;
  unknown ones stay in the dialog with a status message. Persists
  (dir, filename) per `persist_key`.
- Generic error modal (`screen_error.cpp`, `ShowError(msg)`): centred
  red-titled popup, dismissable with Esc/Enter. Used by the export
  failures (open-for-write, ODS save, unknown extension/kind);
  ready for adoption elsewhere.
- Per-key path persistence (`SaveLastUsed`/`LoadLastUsed` in
  `shell.cpp`): two-line file per key under the user-data dir.
- `UserDataDir()` extracted from the history path helper so the new
  per-key persistence shares the same XDG/AppData logic.
- New help-screen topic "Export"; user-facing `doc/user/analysis.md`
  gains an "Exporting" section; `DESIGN.md` gains a generics
  section covering the dialog / error modal / persistence / ODS
  writer; `DumpCommandsMd` now respects the `hidden` flag (the
  `connect` alias no longer appears in the auto-gen reference).

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

src/tui/tui.hpp

@@ -84,8 +84,13 @@ class Tui {
     std::string explore_child_filter;
     std::string explore_detail_filter;
     std::vector<std::string> explore_detail;
-    std::vector<std::string> explore_detail_sig;  ///< parallel: signal name per detail line (empty = no signal)
+    std::vector<std::string> explore_detail_sig;  ///< parallel: `module\tsignal` per row (empty = no action)
     int explore_detail_idx;
+    // Second detail sub-panel — populated only when the children pane is on
+    // the signals tab (top = local pins, bottom = net members).
+    std::vector<std::string> explore_detail2;
+    std::vector<std::string> explore_detail2_sig;
+    int explore_detail2_idx = 0;
     std::string explore_header;
     int explore_focus_idx;
 
@@ -103,6 +108,45 @@ class Tui {
     // ---- Dashboard scroll state (0 = top; grows as the user scrolls down) ----
     int dashboard_scroll_offset = 0;
 
+    // ---- Generic error-notification dialog (modal) ----
+    bool error_open = false;
+    std::string error_message;
+
+    // ---- Generic file-picker dialog (modal) ----
+    // Reused for any "pick a path" interaction (export, save, restore, …).
+    // `persist_key` ties the dir + filename to a key persisted under the
+    // user-data directory so the next invocation under the same key
+    // re-opens on the same location. `on_confirm` runs the actual action
+    // when the user accepts a path.
+    //
+    // Optional `filters`: a horizontal selector (Toggle) at the top of
+    // the dialog with (label, extension) pairs. Picking a filter rewrites
+    // the filename's extension to match. The action then dispatches on
+    // extension (the dialog stays format-agnostic).
+public:
+    struct FilenameFilter { std::string label; std::string extension; };
+private:
+    struct FileDialogState {
+        bool open = false;
+        std::string title;
+        std::string persist_key;
+        std::string dir;
+        std::string filename;
+        std::vector<std::string> entries;     ///< rebuilt every frame
+        std::vector<bool> entries_is_dir;
+        int entry_idx = 0;
+        // Focus map (variable: 0=filters [if any], else +1 each next slot):
+        //   filters present → 0=filters 1=entries 2=filename 3=button (4 slots)
+        //   no filters       → 0=entries 1=filename 2=button (3 slots)
+        int focus_idx = 0;
+        std::string status;
+        std::vector<FilenameFilter> filters;
+        std::vector<std::string> filter_labels;  ///< parallel to `filters`
+        int filter_idx = 0;
+        std::function<void(const std::string &)> on_confirm;
+    };
+    FileDialogState file_dialog;
+
     // ---- Help screen state ----
     int help_topic_idx = 0;
     std::vector<std::string> help_topic_names;  ///< populated by BuildHelpScreen
@@ -149,6 +193,11 @@ public:
     void Run();
     void DumpCommandsMd(std::ostream &out) const;
 
+    // Boot-time hook: dispatch a single command exactly as if the user
+    // typed it (e.g. `restore foo.essim` or `source bring-up.essim`).
+    // Call before `Run()` to seed the system before the event loop starts.
+    void BootDispatch(const std::string &raw);
+
 private:
     // Lifecycle (commands.cpp)
     void RegisterCommands();
@@ -197,6 +246,22 @@ private:
     ftxui::Component BuildDashboardScreen();
     ftxui::Component BuildAnalyzeScreen();
     ftxui::Component BuildHelpScreen();
+    ftxui::Component BuildFileDialog();
+    ftxui::Component BuildErrorModal();
+    // Pop a centred modal with `msg` and an OK button. Esc / Enter close
+    // it. Use for actionable failures the user must see (write errors,
+    // bad inputs, etc.) — for normal feedback keep `Print()`.
+    void ShowError(const std::string &msg);
+    // Open the picker modal. `persist_key` controls where the last-used
+    // dir + filename are stored (one tiny file per key under the user
+    // data directory). `on_confirm` runs when the user presses Enter on
+    // the action button — it receives the absolute path the user picked.
+    void OpenFileDialog(std::string title,
+                        std::string persist_key,
+                        std::string default_filename,
+                        std::vector<FilenameFilter> filters,
+                        std::function<void(const std::string &)> on_confirm);
+    void ConfirmFileDialog();
     ftxui::Component BuildSignalTypeModal();
     ftxui::Component BuildPaletteModal();
     // Open palette (resets query/index, builds initial list).