feat(hooks): add setWidgetComponent for custom TUI components

- New ctx.ui.setWidgetComponent(key, factory) method
- Allows custom Component to render as widget without taking focus
- Unlike custom(), widget components render inline above editor
- Components are disposed when cleared or replaced
- Falls back to no-op in RPC/print modes

packages/coding-agent/src/core/hooks/runner.ts

@@ -50,6 +50,7 @@ const noOpUIContext: HookUIContext = {
 	notify: () => {},
 	setStatus: () => {},
 	setWidget: () => {},
+	setWidgetComponent: () => {},
 	custom: async () => undefined as never,
 	setEditorText: () => {},
 	getEditorText: () => "",