feat: add patchConsole, waitUntilRenderFlush, onRender, and maxFps

Add four behavioral surfaces to the runtime:

- patchConsole (default: true): intercepts console.* methods to route
  output through writeToStdout/writeToStderr, preventing frame corruption.
  Disabled in debug mode. Restored before Vue cleanup on teardown.
- waitUntilRenderFlush(): flushes pending throttled renders and waits
  for the stdout write barrier, exposed on TuiApp and testing RenderResult.
- onRender callback: fires after each commit with { renderTime } in ms.
- maxFps option: overrides the scheduler's default 32ms throttle interval
  with 1000/maxFps. The scheduler now accepts a throttleMs option and
  exposes hasPending() for flush coordination.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/testing/src/render.ts

@@ -32,6 +32,7 @@ export interface RenderResult {
   terminal: Terminal;
   unmount(this: void): void;
   waitUntilExit(this: void): Promise<unknown>;
+  waitUntilRenderFlush(this: void): Promise<void>;
 }
 
 function trimFrame(raw: string): string {
@@ -132,5 +133,6 @@ export async function render(
     terminal,
     unmount: app.unmount.bind(app),
     waitUntilExit: app.waitUntilExit.bind(app),
+    waitUntilRenderFlush: app.waitUntilRenderFlush.bind(app),
   };
 }