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/custom-tools/loader.ts

@@ -7,7 +7,6 @@
  * for custom tools that depend on pi packages.
  */
 
-import { spawn } from "node:child_process";
 import * as fs from "node:fs";
 import { createRequire } from "node:module";
 import * as os from "node:os";
@@ -15,15 +14,10 @@ import * as path from "node:path";
 import { fileURLToPath } from "node:url";
 import { createJiti } from "jiti";
 import { getAgentDir, isBunBinary } from "../../config.js";
+import type { ExecOptions } from "../exec.js";
+import { execCommand } from "../exec.js";
 import type { HookUIContext } from "../hooks/types.js";
-import type {
-	CustomToolFactory,
-	CustomToolsLoadResult,
-	ExecOptions,
-	ExecResult,
-	LoadedCustomTool,
-	ToolAPI,
-} from "./types.js";
+import type { CustomToolFactory, CustomToolsLoadResult, LoadedCustomTool, ToolAPI } from "./types.js";
 
 // Create require function to resolve module paths at runtime
 const require = createRequire(import.meta.url);
@@ -87,88 +81,6 @@ function resolveToolPath(toolPath: string, cwd: string): string {
 	return path.resolve(cwd, expanded);
 }
 
-/**
- * Execute a command and return stdout/stderr/code.
- * Supports cancellation via AbortSignal and timeout.
- */
-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,
-			stdio: ["ignore", "pipe", "pipe"],
-		});
-
-		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: stderr || err.message,
-				code: 1,
-				killed,
-			});
-		});
-	});
-}
-
 /**
  * Create a no-op UI context for headless modes.
  */