🤖 Fix double-close error by using 'using' pattern for directory handles

Replace try/finally with 'using' declaration for automatic resource cleanup.
This prevents ERR_DIR_CLOSED errors when the async iterator auto-closes
the directory handle and then finally block tries to close it again.

Key changes:
- Wrap Dir in AsyncDisposable object with Symbol.asyncDispose
- Use Promise.resolve() to handle Bun's synchronous close() behavior
- Properly catch errors if handle is already closed
- Tests verify correct cleanup in all scenarios (early break, full iteration)

The 'using' pattern ensures cleanup happens at scope exit, even with
early returns or exceptions, while gracefully handling double-close.

Author: ammar-agent

src/services/tools/file_list.ts

@@ -166,17 +166,28 @@ export function createFileListTool(config: { cwd: string }) {
           return { entries: [], totalCount: currentCount.value, exceeded: true };
         }
 
-        // Use opendir for iterative reading - more memory efficient and allows early termination
-        let dirHandle;
         const dirents = [];
         try {
-          dirHandle = await fs.opendir(dir);
-          
+          const dirObj = await fs.opendir(dir);
+          // Use opendir for iterative reading - more memory efficient and allows early termination
+          // Wrap in AsyncDisposable for automatic cleanup via 'using'
+          await using dirHandle = {
+            dir: dirObj,
+            async [Symbol.asyncDispose]() {
+              try {
+                // close() may return void or Promise depending on runtime
+                await Promise.resolve(dirObj.close());
+              } catch {
+                // Ignore errors if already closed (e.g., by iterator completion)
+              }
+            },
+          };
+
           // Read directory entries iteratively to avoid allocating large arrays
           // and to allow early termination if we reach the limit
-          for await (const dirent of dirHandle) {
+          for await (const dirent of dirHandle.dir) {
             dirents.push(dirent);
-            
+
             // Early termination: stop reading if we've collected enough entries
             // (accounts for filtering, so we read a bit more than the limit)
             if (dirents.length > options.maxEntries * 2) {
@@ -186,11 +197,6 @@ export function createFileListTool(config: { cwd: string }) {
         } catch {
           // If we can't read the directory (permissions, etc.), skip it
           return { entries: [], totalCount: currentCount.value, exceeded: false };
-        } finally {
-          // Always close the directory handle
-          if (dirHandle) {
-            await dirHandle.close();
-          }
         }
 
         // Sort: directories first, then files, alphabetically within each group