feat(coding-agent): add ctx.ui.setEditorComponent() extension API

- Add setEditorComponent() to ctx.ui for custom editor components
- Add CustomEditor base class for extensions (handles app keybindings)
- Add keybindings parameter to ctx.ui.custom() factory (breaking change)
- Add modal-editor.ts example (vim-like modes)
- Add rainbow-editor.ts example (animated text highlighting)
- Update docs: extensions.md, tui.md Pattern 7
- Clean up terminal on TUI render errors

packages/coding-agent/examples/extensions/tools.ts

@@ -69,7 +69,7 @@ export default function toolsExtension(pi: ExtensionAPI) {
 			// Refresh tool list
 			allTools = pi.getAllTools();
 
-			await ctx.ui.custom((tui, theme, done) => {
+			await ctx.ui.custom((tui, theme, _kb, done) => {
 				// Build settings items for each tool
 				const items: SettingItem[] = allTools.map((tool) => ({
 					id: tool,