fix(tui): fixed terminal shrink semantics to preserve immutable committed scrollback

- Handled frame shrink by re-anchoring windowTop and chunkTo at commit boundaries.
- Reset committedRows when the frame shrank into committed content to keep history immutable.
- Treated geometryChanged like overlay when advancing chunkTo to stabilize repaint commit timing.
- Updated regressions to assert stable scrollback prefixes and no clear-home/dclear repaint bytes.

packages/coding-agent/test/input-controller-skill-queue.test.ts

@@ -483,7 +483,7 @@ function createEventControllerFixtureForE10() {
 	const ctx = {
 		isInitialized: true,
 		init: vi.fn(async () => {}),
-		ui: { requestRender, setEagerNativeScrollbackRebuild: vi.fn() },
+		ui: { requestRender },
 		statusLine: { invalidate: vi.fn() },
 		updateEditorTopBorder: vi.fn(),
 		addMessageToChat,