feat: add platform adapter structure for V4

- Create adapters/types.js with comprehensive type definitions
- Create adapters/electron/fs.js for file system operations
- Prepare structure for future migration to Tauri/Flutter

This abstraction layer makes future platform migration easier
and enables better testing with mock adapters.

Amit Haridas

src/adapters/electron/fs.js

@@ -0,0 +1,107 @@
+/**
+ * Electron File System Adapter
+ *
+ * Implements file system operations for Electron using IPC.
+ * This abstracts file operations to enable easier testing and migration.
+ *
+ * @version 4.1.0
+ */
+
+/**
+ * Electron File System Adapter
+ * @type {import('../types').FileSystemAdapter}
+ */
+const electronFsAdapter = {
+    /**
+     * Read file content
+     * @param {string} path - File path
+     * @returns {Promise<string>} File content
+     */
+    async readFile(path) {
+        return await window.electronAPI.readFile(path);
+    },
+
+    /**
+     * Write content to file
+     * @param {string} path - File path
+     * @param {string} content - File content
+     * @returns {Promise<void>}
+     */
+    async writeFile(path, content) {
+        return await window.electronAPI.writeFile(path, content);
+    },
+
+    /**
+     * Delete file
+     * @param {string} path - File path
+     * @returns {Promise<void>}
+     */
+    async deleteFile(path) {
+        // TODO: Add IPC channel for delete
+        throw new Error('deleteFile not implemented');
+    },
+
+    /**
+     * Ensure directory exists
+     * @param {string} path - Directory path
+     * @returns {Promise<void>}
+     */
+    async ensureDir(path) {
+        // TODO: Add IPC channel for ensureDir
+        throw new Error('ensureDir not implemented');
+    },
+
+    /**
+     * List directory contents
+     * @param {string} path - Directory path
+     * @returns {Promise<Array<import('../types').FileInfo>>}
+     */
+    async listDirectory(path) {
+        // TODO: Add IPC channel for listDirectory
+        throw new Error('listDirectory not implemented');
+    },
+
+    /**
+     * Check if path exists
+     * @param {string} path - Path to check
+     * @returns {Promise<boolean>}
+     */
+    async exists(path) {
+        // TODO: Add IPC channel for exists
+        throw new Error('exists not implemented');
+    },
+
+    /**
+     * Check if path is a directory
+     * @param {string} path - Path to check
+     * @returns {Promise<boolean>}
+     */
+    async isDirectory(path) {
+        // TODO: Add IPC channel for isDirectory
+        throw new Error('isDirectory not implemented');
+    },
+
+    /**
+     * Copy file or directory
+     * @param {string} source - Source path
+     * @param {string} dest - Destination path
+     * @returns {Promise<void>}
+     */
+    async copy(source, dest) {
+        // TODO: Add IPC channel for copy
+        throw new Error('copy not implemented');
+    },
+
+    /**
+     * Move file or directory
+     * @param {string} source - Source path
+     * @param {string} dest - Destination path
+     * @returns {Promise<void>}
+     */
+    async move(source, dest) {
+        // TODO: Add IPC channel for move
+        throw new Error('move not implemented');
+    }
+};
+
+module.exports = { electronFsAdapter };