Add todo hook companion to todo custom tool

- /todos command displays all todos on current branch with custom UI
- Update hooks.md to clarify components must not be wrapped in Box/Container
- Cross-reference tool and hook in example READMEs

packages/coding-agent/docs/hooks.md

@@ -465,10 +465,12 @@ const result = await ctx.ui.custom((tui, theme, done) => {
   
   doWork(loader.signal).then(done).catch(() => done(null));
   
-  return loader;
+  return loader;  // Return the component directly, do NOT wrap in Box/Container
 });
 ```
 
+**Important:** Return your component directly from the callback. Do not wrap it in a `Box` or `Container`, as this breaks input handling.
+
 Your component can:
 - Implement `handleInput(data: string)` to receive keyboard input
 - Implement `render(width: number): string[]` to render lines