feat(coding-agent): add assistant thinking renderers

packages/coding-agent/examples/extensions/README.md

@@ -41,6 +41,7 @@ cp permission-gate.ts ~/.omp/agent/extensions/
 | `handoff.ts`     | Transfer context to a new focused session via `/handoff <goal>`                |
 | `qna.ts`         | Extracts questions from last response into editor via `ctx.ui.setEditorText()` |
 | `status-line.ts` | Shows turn progress in footer via `ctx.ui.setStatus()` with themed colors      |
+| `thinking-note.ts` | Adds display-only supplemental UI below assistant thinking blocks              |
 | `snake.ts`       | Snake game with custom UI, keyboard handling, and session persistence          |
 
 ### Git Integration

packages/coding-agent/examples/extensions/thinking-note.ts

@@ -0,0 +1,13 @@
+import type { ExtensionFactory } from "@oh-my-pi/pi-coding-agent";
+import { Container, Text } from "@oh-my-pi/pi-tui";
+
+const extension: ExtensionFactory = pi => {
+	pi.setLabel("Thinking note");
+	pi.registerAssistantThinkingRenderer((context, theme) => {
+		const container = new Container();
+		container.addChild(new Text(theme.fg("dim", `thinking chars: ${context.text.length}`), 1, 0));
+		return container;
+	});
+};
+
+export default extension;