Add a configurable "Re-detect Focus" reload action

[t-h-tech]

Summary

Cotabby sometimes latches onto the wrong focus source — it keeps a plain AX text field (e.g. an editor pane) instead of the terminal shell prompt or the Claude Code TUI, because the editor-protection guards key off a focus snapshot that can go stale. This adds a manual escape hatch (a configurable "Re-detect Focus" reload action, available as both a global hotkey and a menu-bar item) plus a low-risk automatic mitigation (re-read focus on app activation).

What the reload does, in order: prune dead shell sessions → cancel in-flight TUI OCR and release a TUI-owned injection → stop AX suppression and republish the real focused element → drop stale prompt anchors → force an immediate fresh AX read → re-evaluate suggestion availability. After that, the next shell report / TUI heartbeat / keystroke re-injects the correct source because the stale snapshot that was blocking it is gone.

Validation

xcodebuild test -project Cotabby.xcodeproj -scheme Cotabby \
  -destination 'platform=macOS' CODE_SIGNING_ALLOWED=NO
# ** TEST SUCCEEDED **  793 tests, 4 skipped, 0 failures
#   incl. ReloadFocusKeybindTests (3) and the new .reloadFocus ShortcutConflictTests

swiftlint lint --quiet
# exit 0 — no violations

xcodegen generate && git diff --exit-code -- Cotabby.xcodeproj
# clean — committed project matches project.yml (new test file wired in)

Manual: built + ran from Xcode; bound the hotkey in Settings → Shortcuts, confirmed it fires the reload, and confirmed the menu-bar "Re-detect Focus" item triggers the same path. App-activation auto-refresh re-resolves the focused source when switching back into a terminal/editor pane without pressing reload.

Linked issues

None.

Risk / rollout notes

• Opt-in by default. The hotkey ships unbound (shows "None"); users with no binding pay no per-keystroke tap cost and see no behavior change. The menu-bar item and app-switch auto-refresh are the only always-on surfaces.
• Settings migration is additive. Three new UserDefaults keys (cotabbyReloadFocusKeyCode / Modifiers / Label), all defaulting to the disabled sentinel. No existing keys touched.
• App-activation observer does a focus re-read on every app switch; FocusTracker debounces by focused-element identity, so this is cheap. The observer is owned by AppDelegate (app-lifetime), not the transient environment.
• Project file: Cotabby.xcodeproj/project.pbxproj was regenerated with xcodegen generate to wire in the new test (the only change is the four standard entries for ReloadFocusKeybindTests.swift; no signing/team or other drift).