Custom tools with session lifecycle, examples for hooks and tools

- Custom tools: TypeScript modules that extend pi with new tools
  - Custom TUI rendering via renderCall/renderResult
  - User interaction via pi.ui (select, confirm, input, notify)
  - Session lifecycle via onSession callback for state reconstruction
  - Examples: todo.ts, question.ts, hello.ts

- Hook examples: permission-gate, git-checkpoint, protected-paths

- Session lifecycle centralized in AgentSession
  - Works across all modes (interactive, print, RPC)
  - Unified session event for hooks (replaces session_start/session_switch)

- Box component added to pi-tui

- Examples bundled in npm and binary releases

Fixes #190

packages/coding-agent/src/core/settings-manager.ts

@@ -36,6 +36,7 @@ export interface Settings {
 	collapseChangelog?: boolean; // Show condensed changelog after update (use /changelog for full)
 	hooks?: string[]; // Array of hook file paths
 	hookTimeout?: number; // Timeout for hook execution in ms (default: 30000)
+	customTools?: string[]; // Array of custom tool file paths
 	skills?: SkillsSettings;
 	terminal?: TerminalSettings;
 }
@@ -231,6 +232,15 @@ export class SettingsManager {
 		this.save();
 	}
 
+	getCustomToolPaths(): string[] {
+		return this.settings.customTools ?? [];
+	}
+
+	setCustomToolPaths(paths: string[]): void {
+		this.settings.customTools = paths;
+		this.save();
+	}
+
 	getSkillsEnabled(): boolean {
 		return this.settings.skills?.enabled ?? true;
 	}