Refactor: shared exec utility, rename CustomMessageRenderer to HookMessageRenderer

- Extract execCommand to src/core/exec.ts, shared by hooks and custom-tools
- Rename CustomMessageRenderer -> HookMessageRenderer
- Rename registerCustomMessageRenderer -> registerMessageRenderer
- Renderer now receives HookMessage instead of CustomMessageEntry
- CustomMessageComponent now has setExpanded() and responds to Ctrl+E toggle
- Re-export ExecOptions/ExecResult from exec.ts for backward compatibility

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

@@ -2,17 +2,14 @@
  * Hook runner - executes hooks and manages their lifecycle.
  */
 
-import { spawn } from "node:child_process";
 import type { ModelRegistry } from "../model-registry.js";
 import type { SessionManager } from "../session-manager.js";
 import type { AppendEntryHandler, LoadedHook, SendMessageHandler } from "./loader.js";
 import type {
-	CustomMessageRenderer,
-	ExecOptions,
-	ExecResult,
 	HookError,
 	HookEvent,
 	HookEventContext,
+	HookMessageRenderer,
 	HookUIContext,
 	RegisteredCommand,
 	SessionEvent,
@@ -32,78 +29,8 @@ const DEFAULT_TIMEOUT = 30000;
  */
 export type HookErrorListener = (error: HookError) => void;
 
-/**
- * Execute a command and return stdout/stderr/code.
- * Supports cancellation via AbortSignal and timeout.
- */
-export async function execCommand(
-	command: string,
-	args: string[],
-	cwd: string,
-	options?: ExecOptions,
-): Promise<ExecResult> {
-	return new Promise((resolve) => {
-		const proc = spawn(command, args, { cwd, shell: false });
-
-		let stdout = "";
-		let stderr = "";
-		let killed = false;
-		let timeoutId: NodeJS.Timeout | undefined;
-
-		const killProcess = () => {
-			if (!killed) {
-				killed = true;
-				proc.kill("SIGTERM");
-				// Force kill after 5 seconds if SIGTERM doesn't work
-				setTimeout(() => {
-					if (!proc.killed) {
-						proc.kill("SIGKILL");
-					}
-				}, 5000);
-			}
-		};
-
-		// Handle abort signal
-		if (options?.signal) {
-			if (options.signal.aborted) {
-				killProcess();
-			} else {
-				options.signal.addEventListener("abort", killProcess, { once: true });
-			}
-		}
-
-		// Handle timeout
-		if (options?.timeout && options.timeout > 0) {
-			timeoutId = setTimeout(() => {
-				killProcess();
-			}, options.timeout);
-		}
-
-		proc.stdout?.on("data", (data) => {
-			stdout += data.toString();
-		});
-
-		proc.stderr?.on("data", (data) => {
-			stderr += data.toString();
-		});
-
-		proc.on("close", (code) => {
-			if (timeoutId) clearTimeout(timeoutId);
-			if (options?.signal) {
-				options.signal.removeEventListener("abort", killProcess);
-			}
-			resolve({ stdout, stderr, code: code ?? 0, killed });
-		});
-
-		proc.on("error", (_err) => {
-			if (timeoutId) clearTimeout(timeoutId);
-			if (options?.signal) {
-				options.signal.removeEventListener("abort", killProcess);
-			}
-			resolve({ stdout, stderr, code: 1, killed });
-		});
-	});
-}
+// Re-export execCommand for backward compatibility
+export { execCommand } from "../exec.js";
 
 /**
  * Create a promise that rejects after a timeout.
@@ -241,12 +168,12 @@ export class HookRunner {
 	}
 
 	/**
-	 * Get a custom message renderer for the given customType.
+	 * Get a message renderer for the given customType.
 	 * Returns the first renderer found across all hooks, or undefined if none.
 	 */
-	getCustomMessageRenderer(customType: string): CustomMessageRenderer | undefined {
+	getMessageRenderer(customType: string): HookMessageRenderer | undefined {
 		for (const hook of this.hooks) {
-			const renderer = hook.customMessageRenderers.get(customType);
+			const renderer = hook.messageRenderers.get(customType);
 			if (renderer) {
 				return renderer;
 			}