feat(notifications): add notification history panel and overlay UX fixes

- New toggleNotificationHistory (Ctrl+N) session-scoped history panel; slides in from same edge as notification stack
- Overlay error/recovery toast follows notifications.overlayPosition; stack and history side seeded at startup
- Cold managed background startup initializes tray and visible overlay shell before tokenization warmups finish
- Add Update button to overlay update-available notifications
- Fix Ctrl+S sentence-card flow: only Anki progress notification, no duplicate status toast
- Fix overlay notification close/actions clickability above subtitle bars on Linux
- Increase pause-until-ready default timeout from 15s to 30s

src/shared/ipc/validators.test.ts

@@ -0,0 +1,44 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+
+import { DEFAULT_CONFIG, DEFAULT_KEYBINDINGS } from '../../config/definitions';
+import { compileSessionBindings } from '../../core/services/session-bindings';
+import { resolveConfiguredShortcuts } from '../../core/utils/shortcut-config';
+import { parseSessionActionDispatchRequest } from './validators';
+
+// Regression guard: SESSION_ACTION_IDS in validators.ts is a hand-maintained mirror of the
+// SessionActionId union. If a new shortcut-backed action is added to the union/defaults but not to
+// the validator allow-list, the renderer's dispatchSessionAction IPC is rejected at runtime (which
+// surfaces as a "Renderer error recovered" toast). Compile every default binding and assert the
+// validator accepts each one so the two lists can't silently drift apart.
+test('every default session-action binding is accepted by parseSessionActionDispatchRequest', () => {
+  const { bindings } = compileSessionBindings({
+    shortcuts: resolveConfiguredShortcuts(DEFAULT_CONFIG, DEFAULT_CONFIG),
+    keybindings: DEFAULT_KEYBINDINGS,
+    statsToggleKey: DEFAULT_CONFIG.stats.toggleKey,
+    statsMarkWatchedKey: DEFAULT_CONFIG.stats.markWatchedKey,
+    platform: 'linux',
+    rawConfig: DEFAULT_CONFIG,
+  });
+
+  const sessionActions = bindings.filter((binding) => binding.actionType === 'session-action');
+  assert.ok(sessionActions.length > 0, 'expected default session-action bindings to exist');
+
+  for (const binding of sessionActions) {
+    if (binding.actionType !== 'session-action') continue;
+    const request =
+      binding.payload === undefined
+        ? { actionId: binding.actionId }
+        : { actionId: binding.actionId, payload: binding.payload };
+    assert.ok(
+      parseSessionActionDispatchRequest(request) !== null,
+      `validator rejected session action: ${binding.actionId}`,
+    );
+  }
+});
+
+test('toggleNotificationHistory dispatch request is accepted', () => {
+  assert.deepEqual(parseSessionActionDispatchRequest({ actionId: 'toggleNotificationHistory' }), {
+    actionId: 'toggleNotificationHistory',
+  });
+});