feat(filesystem): add copy_file tool for efficient file/directory copying

Implements a new copy_file tool that addresses issue #1581 by providing an efficient way to copy files and directories without requiring read/write operations for large files.

## Changes:
- Add copy_file tool with support for both files and directories
- Use fs.copyFile for files (optimized for large files)
- Use fs.cp with recursive option for directories
- Include proper validation and error handling
- Update README documentation

## Implementation Details:
- Validates both source and destination paths are within allowed directories
- Checks if destination exists and fails appropriately
- Follows existing tool patterns for consistency
- Maintains security checks and path validation

Fixes #1581

Author: nandsha

src/filesystem/README.md

@@ -71,6 +71,14 @@ Node.js server implementing Model Context Protocol (MCP) for filesystem operatio
     - `destination` (string)
   - Fails if destination exists
 
+- **copy_file**
+  - Copy a file or directory from source to destination
+  - Inputs:
+    - `source` (string)
+    - `destination` (string)
+  - For directories, copies all contents recursively
+  - Fails if destination exists
+
 - **search_files**
   - Recursively search for files/directories
   - Inputs:

src/filesystem/index.ts

@@ -136,6 +136,11 @@ const MoveFileArgsSchema = z.object({
   destination: z.string(),
 });
 
+const CopyFileArgsSchema = z.object({
+  source: z.string(),
+  destination: z.string(),
+});
+
 const SearchFilesArgsSchema = z.object({
   path: z.string(),
   pattern: z.string(),
@@ -369,6 +374,13 @@ server.setRequestHandler(ListToolsRequestSchema, async () => {
           "Only works within allowed directories.",
         inputSchema: zodToJsonSchema(EditFileArgsSchema) as ToolInput,
       },
+      {
+        name: "copy_file",
+        description:
+          "Copy a file or directory from source to destination. For directories, copies all contents recursively. " +
+          "If destination exists, the operation will fail. Both source and destination must be within allowed directories.",
+        inputSchema: zodToJsonSchema(CopyFileArgsSchema) as ToolInput,
+      },
       {
         name: "create_directory",
         description:
@@ -612,6 +624,41 @@ server.setRequestHandler(CallToolRequestSchema, async (request) => {
         };
       }
 
+      case "copy_file": {
+        const parsed = CopyFileArgsSchema.safeParse(args);
+        if (!parsed.success) {
+          throw new Error(`Invalid arguments for copy_file: ${parsed.error}`);
+        }
+        const validSourcePath = await validatePath(parsed.data.source);
+        const validDestPath = await validatePath(parsed.data.destination);
+        
+        // Check if destination already exists
+        try {
+          await fs.access(validDestPath);
+          throw new Error(`Destination already exists: ${parsed.data.destination}`);
+        } catch (error) {
+          // If error is NOT about file not existing, re-throw it
+          if (error instanceof Error && !error.message.includes('ENOENT')) {
+            throw error;
+          }
+        }
+        
+        // Check if source is a directory
+        const sourceStats = await fs.stat(validSourcePath);
+        
+        if (sourceStats.isDirectory()) {
+          // For directories, use fs.cp with recursive option
+          await fs.cp(validSourcePath, validDestPath, { recursive: true });
+        } else {
+          // For files, use copyFile which is optimized for large files
+          await fs.copyFile(validSourcePath, validDestPath);
+        }
+        
+        return {
+          content: [{ type: "text", text: `Successfully copied ${parsed.data.source} to ${parsed.data.destination}` }],
+        };
+      }
+
       case "list_allowed_directories": {
         return {
           content: [{