Fixes #5252: Handle images without data URI format in access_mcp_resource

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Summary

This PR fixes issue #5252 where the access_mcp_resource function fails to handle images that don't use the standard data:image/;base64,base64string format.

Problem

Most image resources in MCP servers don't use the data URI format, causing image processing to fail when the system expects all images to be in data:image/png;base64,base64string format.

Solution

Changes Made

1. Modified accessMcpResourceTool.ts (lines 71-87):

   • Added logic to detect if blob data is already in data URI format
   • Converts raw base64 data to proper data URI format with appropriate MIME type
   • Maintains backward compatibility with existing data URI format

2. Updated formatImagesIntoBlocks in responses.ts (lines 179-203):

   • Enhanced to handle both data URI and raw base64 formats
   • Extracts MIME type from data URI or defaults to 'image/png' for raw base64
   • Preserves existing functionality for standard data URI format

3. Added comprehensive test suite (responses-image-handling.spec.ts):

   • Tests standard data URI format handling
   • Tests raw base64 data handling
   • Tests mixed format scenarios
   • Tests different MIME types (PNG, JPEG, GIF, WebP)
   • Tests edge cases (empty arrays, undefined inputs)

Technical Details

• Backward Compatible: Existing data URI format continues to work unchanged
• MIME Type Handling: Preserves original MIME types from data URIs, defaults to 'image/png' for raw base64
• Format Detection: Uses regex pattern to detect data URI vs raw base64 format
• Error Handling: Graceful fallback to default MIME type if parsing fails

Testing

• ✅ All new tests pass (9 test cases)
• ✅ Linting passes
• ✅ Type checking passes
• ✅ Maintains backward compatibility

Fixes

Closes #5252

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Important

Fixes image handling in accessMcpResourceTool to support both data URI and raw base64 formats, with comprehensive tests added.

• Behavior:
  • accessMcpResourceTool in accessMcpResourceTool.ts now detects if image blobs are in data URI format and converts raw base64 data to data URI with MIME type.
  • formatImagesIntoBlocks in responses.ts enhanced to handle both data URI and raw base64 formats, defaulting to 'image/png' for raw base64.
• Testing:
  • New test suite responses-image-handling.spec.ts added to test standard data URI, raw base64, mixed formats, and different MIME types.
• Misc:
  • Maintains backward compatibility with existing data URI format.

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[delve-auditor]

✅ No security or compliance issues detected. Reviewed everything up to 86e5ff3.

Security Overview

• 🔎 Scanned files: 3 changed file(s)

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