feat: add config and keybindings for new ink terminal buffer mode

test: update test utils and resolve snapshot differences for ink changes

feat: refactor VirtualizedList to support static rendering and terminal buffers

feat: wire up AppContainer mouse mode and recording state for ink buffer

Fix stale ref in ScrollProvider breaking scrolling.

The ScrollProvider was getting stuck with a stale reference because the
`scrollables` Map was being registered and unregistered whenever the entry
identity changed. The underlying `ScrollableList` component dynamically created
a new ID which caused React remount cycles, while the `ScrollProvider` itself
suffered from state lag where the event handler ref was one tick behind the
actual registration.

This commit resolves these issues by:
1. Adding a stable `id` and `key` to `ScrollableList` in `MainContent.tsx`
2. Making `scrollablesRef` synchronously update in `ScrollProvider.tsx`
3. Using a proxy entry in `useScrollable` to avoid constant re-registering.

chore: add useEffect cleanup for ResizeObservers

Checkpoint fixing terminal buffer support.

Termina Serializer Optimization

packages/cli/src/ui/components/ExitPlanModeDialog.test.tsx

@@ -166,6 +166,7 @@ Implement a comprehensive authentication system with multiple providers.
             writeTextFile: vi.fn(),
           }),
           getUseAlternateBuffer: () => useAlternateBuffer,
+          getUseTerminalBuffer: () => false,
         } as unknown as import('@google/gemini-cli-core').Config,
         settings: createMockSettings({ ui: { useAlternateBuffer } }),
       },
@@ -466,6 +467,7 @@ Implement a comprehensive authentication system with multiple providers.
                   writeTextFile: vi.fn(),
                 }),
                 getUseAlternateBuffer: () => useAlternateBuffer ?? true,
+                getUseTerminalBuffer: () => false,
               } as unknown as import('@google/gemini-cli-core').Config,
               settings: createMockSettings({
                 ui: { useAlternateBuffer: useAlternateBuffer ?? true },