Global hotkey, Settings window, launch at login

[Saber5656]

Source of truth: docs/issues/22-app-hotkey-settings.md in this repository (see PR #1 until merged). If this issue and the draft diverge, the draft wins.

Summary

Add the configurable global hotkey (default ⌃⌥⌘M → Capture Region) via
KeyboardShortcuts, the three-tab Settings window bound to the shared config file with
live reload, and launch-at-login via SMAppService.

Context

DESIGN §9.6 defines the Settings surface; ADR-006 puts all settings except the hotkey in
config.json (the hotkey lives in KeyboardShortcuts' own store). KU-4 tracks the
dependency pin.

Scope

• App/ScanMD/Settings/ (GeneralTab.swift, OCRTab.swift, ShortcutsTab.swift,
  SettingsView.swift), HotkeyManager.swift, ConfigStore.swift (observable bridge +
  file watcher), login item wiring.

Detailed Requirements

1. Hotkey: KeyboardShortcuts.Name("captureRegion") with default ⌃⌥⌘M;
   HotkeyManager registers on launch and calls
   CaptureCoordinator.shared.request(.region). Busy state → coordinator's beep-drop
   already applies. Recording UI = KeyboardShortcuts.Recorder in the Shortcuts tab.
   Pin the package exact to a version verified against macOS 14 (record the verified
   version in the PR → resolves KU-4; if incompatible, STOP and open the Carbon-wrapper
   follow-up issue per ISSUE_PLAN KU-4 contingency before proceeding).
2. ConfigStore (@MainActor ObservableObject):
   • loads via ConfigLoader (Issue 06); publishes typed bindings for the §9.6 controls;
   • saves through ConfigLoader.save (atomic, 0600) with 500 ms debounce;
   • watches the file via DispatchSource.makeFileSystemObjectSource (vnode write/
     delete/rename on the containing directory to survive atomic replaces); external
     change → reload + republish (last-writer-wins, no merge — ADR-006);
   • reload storms guarded (ignore events within 200 ms after own save).
3. General tab: copy-to-clipboard toggle disabled+on with caption "always on in
   v1" · auto-save toggle + folder picker (NSOpenPanel.canChooseDirectories, path
   stored in output.directory) · notification toggle (app.showNotification) ·
   launch-at-login toggle → SMAppService.mainApp.register()/unregister(), reflecting
   status on appear (handle .requiresApproval by showing a hint linking to Login
   Items settings).
4. OCR tab: language priority editable list seeded from ocr.languages (reorder via
   drag, add via validated text field using Issue 08's validate(languages:), remove;
   minimum one language) · auto-detect toggle · accurate/fast picker.
5. Shortcuts tab: the Recorder + a static hint that CLI users can bind
   scanmd in Raycast/Shortcuts too.
6. Captures pick up changed config immediately (Issue 20 reads per capture — verify).
7. Tests: ConfigStore round-trip (edit → debounce save → file content), external-edit
   reload (rewrite file in test → published values change), storm guard, login-item
   calls behind a SMAppServicing fake. UI tabs are manual.
8. Manual checklist: hotkey fires from any app (incl. full-screen apps — record
   result) · re-recording the shortcut takes effect immediately and survives relaunch ·
   every General/OCR control round-trips to config.json (show file diff) · editing
   config.json in a text editor while Settings is open updates the UI · launch at
   login works after logout/login (or .requiresApproval path documented) · CLI sees
   the same config changes (scanmd config path + a capture honoring changed
   languages).

Acceptance Criteria

• Hotkey default ⌃⌥⌘M works and is re-recordable; KU-4 resolved with a pinned,
  verified version.
• Settings tabs match DESIGN §9.6 exactly (controls, bindings, disabled states).
• Config file remains the single source of truth (no shadow UserDefaults except
  KeyboardShortcuts' own store) — code-reviewed grep for UserDefaults.
• Store tests green; manual checklist evidence attached.

Validation

swift test --filter ConfigStoreTests + manual checklist + config-diff transcript.

Dependencies

Issues 06, 19.

Non-goals

Per-capture-kind hotkeys (v2), menu customization, localization (v2), notification
content settings beyond the toggle.

Design References

DESIGN §9.5, §9.6, §8.7; ADR-006; ISSUE_PLAN KU-4.