🤖 Check workdir exists before spawning in LocalRuntime

Root cause of 'spawn bash ENOENT' was that the working directory
didn't exist when spawn() was called. Node.js throws ENOENT when
you try to spawn with a non-existent cwd.

Now we check if the workdir exists before spawning and throw a clear
error message if it doesn't. This prevents confusing ENOENT errors.

Author: ammar-agent

src/runtime/LocalRuntime.ts

@@ -36,6 +36,19 @@ export class LocalRuntime implements Runtime {
   exec(command: string, options: ExecOptions): ExecStream {
     const startTime = performance.now();
 
+    // Determine working directory
+    const cwd = options.cwd ?? this.workdir;
+
+    // Verify working directory exists before spawning
+    // If it doesn't exist, spawn will fail with ENOENT which is confusing
+    if (!fs.existsSync(cwd)) {
+      throw new RuntimeErrorClass(
+        `Working directory does not exist: ${cwd}`,
+        "exec",
+        new Error(`ENOENT: no such file or directory, stat '${cwd}'`)
+      );
+    }
+
     // Find bash path (important for CI environments where PATH may not be set)
     const bashPath = findBashPath();
     const nicePath = findNicePath();
@@ -48,7 +61,7 @@ export class LocalRuntime implements Runtime {
         : ["-c", command];
 
     const childProcess = spawn(spawnCommand, spawnArgs, {
-      cwd: options.cwd ?? this.workdir,
+      cwd,
       env: {
         ...process.env,
         ...(options.env ?? {}),