Read and write files through Zed (#6169)

Co-authored-by: Agus Zubiaga <agus@zed.dev>

packages/core/src/services/fileSystemService.ts

@@ -0,0 +1,41 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import fs from 'fs/promises';
+
+/**
+ * Interface for file system operations that may be delegated to different implementations
+ */
+export interface FileSystemService {
+  /**
+   * Read text content from a file
+   *
+   * @param filePath - The path to the file to read
+   * @returns The file content as a string
+   */
+  readTextFile(filePath: string): Promise<string>;
+
+  /**
+   * Write text content to a file
+   *
+   * @param filePath - The path to the file to write
+   * @param content - The content to write
+   */
+  writeTextFile(filePath: string, content: string): Promise<void>;
+}
+
+/**
+ * Standard file system implementation
+ */
+export class StandardFileSystemService implements FileSystemService {
+  async readTextFile(filePath: string): Promise<string> {
+    return fs.readFile(filePath, 'utf-8');
+  }
+
+  async writeTextFile(filePath: string, content: string): Promise<void> {
+    await fs.writeFile(filePath, content, 'utf-8');
+  }
+}