feat(settings): replicate the WorkBuddy keyboard shortcuts panel and wire global bindings (TODO 12)

Recover the WorkBuddy 5.8.3 快捷键 page from REA evidence (keyboard-shortcuts-DOrivHwf.css + tokens): 49 recovered module rules, scoped light/dark tokens, the 24-row 命令/按键绑定/操作 sheet (panel 638x620, header 39, scroll 638x533, rows 41/45/44, keycaps 22) and the recording/ESC-cancel interaction.

Wire the panel into SettingsDialog and keep only real bindings honest: 14 of 24 rows are marked supported, the remaining rows stay visually 1:1 but are labelled 尚未接入 and cannot pretend to save custom keys. Add Ctrl+K search focus, Ctrl+B / Ctrl+Shift+B left/right sidebar toggles, Ctrl+N new conversation (App -> Sidebar path) and Esc-to-stop while generating; fix the sidebar search focus race introduced by conditional mounting.

Verify with scripts/verify-shortcuts-settings.cjs: 32 assertions covering geometry, row/key order, search filtering, recording/cancel, supported ids, dark theme surfaces and the four new global shortcuts in a real main window. All existing regressions stay green.

scripts/rea/probe-todo12-shortcuts-interactions.json

@@ -0,0 +1,22 @@
+{
+  "include_fonts": false,
+  "include_message_content": false,
+  "track_selectors": [
+    ".keyboard-shortcuts-panel__toolbar",
+    ".keyboard-shortcuts-panel__search",
+    ".keyboard-shortcuts-panel__list",
+    ".shortcut-item",
+    ".shortcut-item__binding-tooltip-anchor",
+    ".wb-button"
+  ],
+  "actions": [
+    { "kind": "wait", "step_id": "shortcuts-interaction-baseline", "duration_ms": 200, "frames": 1 },
+    { "kind": "text", "step_id": "search-voice-shortcut", "selector": ".keyboard-shortcuts-panel__search input", "text": "语音", "frames": 0 },
+    { "kind": "wait", "step_id": "search-voice-result", "duration_ms": 200, "frames": 1 },
+    { "kind": "text", "step_id": "clear-shortcut-search", "selector": ".keyboard-shortcuts-panel__search input", "text": "", "frames": 0 },
+    { "kind": "wait", "step_id": "search-cleared", "duration_ms": 200, "frames": 1 },
+    { "kind": "click", "step_id": "click-disabled-restore-defaults", "selector": ".keyboard-shortcuts-panel__toolbar .wb-button--disabled", "index": 0, "frames": 1 },
+    { "kind": "click", "step_id": "open-shortcut-key-editor", "selector": "#settings-keyboard-shortcut-open-global-search .shortcut-item__binding-tooltip-anchor", "index": 0, "frames": 1 },
+    { "kind": "key", "step_id": "cancel-shortcut-key-editor", "key": "Escape", "frames": 1 }
+  ]
+}