fix: file @ autocomplete performance using fd

- Replace slow synchronous directory walking with fd for fuzzy file search
- Auto-download fd to ~/.pi/agent/tools/ if not found in PATH
- Performance improved from ~900ms to ~10ms per keystroke on large repos
- Remove minimatch dependency from tui package
- Graceful degradation if fd unavailable (empty results)

Fixes #69

packages/coding-agent/src/tui/tui-renderer.ts

@@ -105,6 +105,7 @@ export class TuiRenderer {
 		changelogMarkdown: string | null = null,
 		newVersion: string | null = null,
 		scopedModels: Array<{ model: Model<any>; thinkingLevel: ThinkingLevel }> = [],
+		fdPath: string | null = null,
 	) {
 		this.agent = agent;
 		this.sessionManager = sessionManager;
@@ -194,6 +195,7 @@ export class TuiRenderer {
 				clearCommand,
 			],
 			process.cwd(),
+			fdPath,
 		);
 		this.editor.setAutocompleteProvider(autocompleteProvider);
 	}