feat: enable MCP tools to handle base64 image uploads

[roomote]

This PR attempts to address Issue #9805. Feedback and guidance are welcome!

Problem

When invoking an MCP tool with an image parameter, the system was passing file paths instead of base64-encoded image data, preventing MCP servers from properly receiving and processing image inputs.

Solution

Modified UseMcpToolTool to automatically detect and convert image file paths to base64 data URLs before passing arguments to MCP servers.

Changes

• Added image file path detection in UseMcpToolTool.ts
• Implemented recursive conversion of image paths to base64 data URLs in tool arguments
• Added support for nested image paths in complex argument objects
• Preserved non-image paths and already-encoded base64 data unchanged
• Added comprehensive test coverage for all image handling scenarios

Implementation Details

1. Image Detection: Checks file extension against supported image formats and verifies file existence
2. Base64 Conversion: Uses existing readImageAsDataUrlWithBuffer helper from imageHelpers.ts
3. Recursive Processing: Handles images in nested objects and arrays within MCP tool arguments
4. Error Handling: Falls back to original value if image conversion fails

Testing

• ✅ All existing tests pass
• ✅ Added 5 new test cases for image handling scenarios
• ✅ Tests cover: basic conversion, nested paths, non-image files, already-encoded data, and error cases

Fixes #9805

[roomote]

Rooviewer   See task on Roo Cloud

Review complete. Found 3 issues that need attention:

• Relative image paths won't resolve correctly - fs.stat() needs path resolution relative to task.cwd
• Missing cwd parameter - helper methods need access to resolve paths properly
• Silent error handling - image conversion failures should notify users via task.say()

_{Mention @roomote in a comment to request specific changes to this pull request or fix all unresolved issues.}

[roomote]

Relative image paths won't be resolved correctly. The fs.stat(value) call on line 61 uses the path as-is without resolving it relative to task.cwd. This means relative paths like "./images/photo.png" will fail the file existence check even if the file exists, preventing conversion to base64. Other tools like ReadFileTool resolve paths with path.resolve(task.cwd, relPath) before checking file existence.

_{Fix it with Roo Code or mention @roomote and request a fix.}

[roomote]

The isImageFilePath and convertImagePathsToBase64 methods need access to task.cwd to properly resolve relative paths, but they don't receive it as a parameter. To fix the path resolution issue, these methods should accept cwd: string as a parameter so they can resolve paths like path.resolve(cwd, value) before calling fs.stat().

_{Fix it with Roo Code or mention @roomote and request a fix.}

[roomote]

Image conversion errors are only logged to console and silently fall back to the original value. Users won't be notified when image conversion fails. Consider using await task.say("error", ...) to report conversion failures to the user, similar to how ReadFileTool handles image errors on line 382.

_{Fix it with Roo Code or mention @roomote and request a fix.}