feat(coding-agent): add hook API for CLI flags, shortcuts, and tool control

Hook API additions:
- pi.getTools() / pi.setTools(toolNames) - dynamically enable/disable tools
- pi.registerFlag(name, options) / pi.getFlag(name) - register custom CLI flags
- pi.registerShortcut(shortcut, options) - register keyboard shortcuts

Plan mode hook (examples/hooks/plan-mode.ts):
- /plan command or Shift+P shortcut to toggle
- --plan CLI flag to start in plan mode
- Read-only tools: read, bash, grep, find, ls
- Bash restricted to non-destructive commands (blocks rm, mv, git commit, etc.)
- Interactive prompt after each response: execute, stay, or refine
- Shows plan indicator in footer when active
- State persists across sessions

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

@@ -168,6 +168,43 @@ export class HookRunner {
 		return this.hooks.map((h) => h.path);
 	}
 
+	/**
+	 * Get all CLI flags registered by hooks.
+	 */
+	getFlags(): Map<string, import("./loader.js").HookFlag> {
+		const allFlags = new Map<string, import("./loader.js").HookFlag>();
+		for (const hook of this.hooks) {
+			for (const [name, flag] of hook.flags) {
+				allFlags.set(name, flag);
+			}
+		}
+		return allFlags;
+	}
+
+	/**
+	 * Set a flag value (after CLI parsing).
+	 */
+	setFlagValue(name: string, value: boolean | string): void {
+		for (const hook of this.hooks) {
+			if (hook.flags.has(name)) {
+				hook.setFlagValue(name, value);
+			}
+		}
+	}
+
+	/**
+	 * Get all keyboard shortcuts registered by hooks.
+	 */
+	getShortcuts(): Map<string, import("./loader.js").HookShortcut> {
+		const allShortcuts = new Map<string, import("./loader.js").HookShortcut>();
+		for (const hook of this.hooks) {
+			for (const [key, shortcut] of hook.shortcuts) {
+				allShortcuts.set(key, shortcut);
+			}
+		}
+		return allShortcuts;
+	}
+
 	/**
 	 * Subscribe to hook errors.
 	 * @returns Unsubscribe function