feat(coding-agent): implement hooks system

- Add hooks infrastructure in core/hooks/ (loader, runner, types)
- HookUIContext interface with mode-specific implementations
- Interactive mode: TUI-based selector/input/confirm dialogs
- RPC mode: JSON protocol for hook UI requests/responses
- Print mode: no-op UI context (hooks run but can't prompt)
- AgentSession.branch() now async, returns { selectedText, skipped }
- Settings: hooks[] and hookTimeout configuration
- Export hook types from package for hook authors

Based on PR #147 proposal, adapted for new architecture.

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

@@ -19,6 +19,8 @@ export interface Settings {
 	hideThinkingBlock?: boolean;
 	shellPath?: string; // Custom shell path (e.g., for Cygwin users on Windows)
 	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)
 }
 
 export class SettingsManager {
@@ -173,4 +175,22 @@ export class SettingsManager {
 		this.settings.collapseChangelog = collapse;
 		this.save();
 	}
+
+	getHookPaths(): string[] {
+		return this.settings.hooks ?? [];
+	}
+
+	setHookPaths(paths: string[]): void {
+		this.settings.hooks = paths;
+		this.save();
+	}
+
+	getHookTimeout(): number {
+		return this.settings.hookTimeout ?? 30000;
+	}
+
+	setHookTimeout(timeout: number): void {
+		this.settings.hookTimeout = timeout;
+		this.save();
+	}
 }