Implement Node.js-compatible Dir API with proper error handling and state management

[Copilot]

This PR implements a complete Node.js-compatible Dir API for memfs, addressing all the requirements outlined in the issue. The implementation now matches Node.js fs.Dir behavior exactly, including proper error handling, state management, and concurrent operation detection.

Key Changes

1. Removed Helper Functions

• Eliminated wrapAsync, isFunction, and promisify helper methods
• Replaced with standard Node.js patterns for consistency

2. Enhanced State Management

• Added closed property to track directory handle state
• Implemented operationQueue for managing concurrent async operations
• Added proper state validation in all methods

3. Comprehensive Error Handling

• Added ERR_DIR_CLOSED error code for operations on closed directories
• Added ERR_DIR_CONCURRENT_OPERATION error code for sync operations during async operations
• Implemented proper error timing using process.nextTick() for callbacks

4. Fixed Path Property

• Changed from getParentPath() to getPath() to return the correct directory path
• Now properly returns the path of the directory being opened, not its parent

5. Improved Method Implementations

Close Operations:

// All three patterns now work correctly with proper error handling
await dir.close();           // Promise-based
dir.close(callback);         // Callback-based  
dir.closeSync();            // Synchronous

Error Handling Examples:

const dir = fs.opendirSync('/test');
dir.closeSync();

// All of these now throw ERR_DIR_CLOSED appropriately
dir.readSync();              // Throws synchronously
await dir.read();            // Rejects promise
dir.read(callback);          // Calls callback with error

Concurrent Operation Detection:

const dir = fs.opendirSync('/test');
dir.read(callback);          // Start async operation
dir.readSync();              // Throws ERR_DIR_CONCURRENT_OPERATION

6. Refactored Async Iterator

• Simplified implementation to use the standard read() method
• Maintains compatibility with for await loops
• Fixed linting issues with proper arrow function usage

Testing

Added comprehensive test suite covering:

• All close operation variants (sync, callback, promise)
• Error conditions for closed directories
• Concurrent operation detection
• Path property validation
• Async iterator functionality

All existing tests continue to pass, ensuring no regressions were introduced.

Compatibility

The implementation now matches Node.js fs.Dir behavior exactly:

• Same error codes and messages
• Same timing for callback errors
• Same state management patterns
• Same concurrent operation handling

Fixes #1087.

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[streamich]

Run yarn prettier and save changes.

[Copilot]

Run yarn prettier and save changes.

Done! Ran yarn prettier and saved the formatting changes. Also fixed a typo in the error message where "operatio ns" was corrected to "operations". Commit: 9fb854d

[streamich]

LGTM

[github-actions]

🎉 This PR is included in version 4.21.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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