fix: harden and de-slop the merged sidebar/chat/settings batch

Post-merge follow-ups for #2740 #2735 #2734 #2690 #2676 #2738 #2684
#2689 #2733 #2739 #2462 #2687 #2736 #2618 #2697, plus three regressions
found while reviewing them:

- ctrl/cmd+digit while typing no longer switches session tabs (#2503 was
  still open in practice: the guard only covered the mod+alt surface binding)
- Shiki template-call sanitizer now covers every bundled grammar, including
  the js/ts aliases and embedding grammars; timed-out highlight requests are
  memoized and no longer cancel unrelated in-flight requests
- settings flush on suspend uses keepalive and also fires on Capacitor
  appStateChange; keeps the selected model persisted across mode switches
- remote-only branches fetch before checkout; range helpers fail clearly
- git status invalidation now fires for runtime adapters too
- settings number inputs and select triggers size in ch so they scale with
  the interface font
- recent-activity timestamps tick from one list-level ticker
- Markdown preview find goes through the shared find_in_file keybind with
  containment, no longer counts its own bar, and debounces observer runs
- #2676 reverted; #2524 fixed by fading the sticky header's own background
  instead of overlaying the content below it
- sticky group headers in the model picker and sidebar render again
  (oc-sticky-fade-scroller class restored after 9b9d7069c)
- project switcher names are left-aligned again (wrapper lost in 26dbc2f30)
- tool card quick-open icon is always visible and opens the same line as the
  expanded card's button
- tautological tests replaced or removed; new oxlint findings fixed

packages/ui/src/lib/persistence.test.ts

@@ -914,6 +914,41 @@ describe('unload lifecycle flush (#2197)', () => {
     }
   });
 
+  test('sends the unload flush with keepalive so the browser cannot cancel it', async () => {
+    // No runtime settings API: the write has to take the HTTP branch, which is
+    // the one the browser cancels on unload without `keepalive`.
+    registerRuntimeAPIs(null);
+    const inits: RequestInit[] = [];
+    const previousFetch = globalThis.fetch;
+    // SAFETY: the mock receives only the (input, init) pair production code
+    // passes and always resolves to a Response; the assertion supplies the
+    // overload signatures a plain arrow function cannot declare.
+    globalThis.fetch = (async (_input, init) => {
+      inits.push(init ?? {});
+      return new Response('{}', { status: 200, headers: { 'Content-Type': 'application/json' } });
+    }) as typeof fetch;
+
+    try {
+      const update = updateDesktopSettings({ gitChangesViewMode: 'flat' });
+      getWindow().dispatchEvent(new Event('pagehide'));
+      await update;
+      await delay(50);
+
+      expect(inits).toHaveLength(1);
+      expect(inits[0].method).toBe('PUT');
+      expect(inits[0].keepalive).toBe(true);
+
+      // The ordinary debounced write stays a plain fetch.
+      inits.length = 0;
+      await updateDesktopSettings({ gitChangesViewMode: 'tree' });
+      await delay(300);
+      expect(inits).toHaveLength(1);
+      expect(inits[0].keepalive).toBe(false);
+    } finally {
+      globalThis.fetch = previousFetch;
+    }
+  });
+
   test('ignores lifecycle events when no settings write is pending', async () => {
     const saveCalls: Array<Partial<SettingsPayload>> = [];
     registerSettingsSave(async (changes) => {