feat(ui): add favorite-model cycling shortcuts (#592)

* feat(ui): add Alt+F / Alt+Shift+F keyboard shortcuts to cycle favorite models

Allows cycling forward/backward through starred models without opening
the model picker. Mirrors the cycle_thinking_variant pattern. Silent
no-op when no models are favorited.

* fix(ui): remap favorite model cycling to ctrl brackets

* chore(ui): update favorite-cycle shortcut comment

packages/ui/src/lib/shortcuts.ts

@@ -291,6 +291,20 @@ const SHORTCUT_ACTIONS: ReadonlyArray<ShortcutAction> = [
     label: 'Cycle thinking variant',
     description: 'Cycle thinking variant while in chat',
   },
+  {
+    id: 'cycle_favorite_model_forward',
+    defaultCombo: 'ctrl+]',
+    label: 'Cycle favorite model forward',
+    description: 'Cycle forward through starred models without opening the picker',
+    customizable: true,
+  },
+  {
+    id: 'cycle_favorite_model_backward',
+    defaultCombo: 'ctrl+[',
+    label: 'Cycle favorite model backward',
+    description: 'Cycle backward through starred models without opening the picker',
+    customizable: true,
+  },
   {
     id: 'expand_input',
     defaultCombo: 'mod+shift+e',