fix(ui): display agent-generated images in response markdown

[kapetr]

Summary

Fixes the display of agent-generated images in response markdown by rewriting their URIs to load the content through the API using the /api/v1/files/{file_id}/content endpoint.

Linked Issues

Resolves #1592

Documentation

• No Docs Needed: minor UI fix

[gemini-code-assist]

Summary of Changes

Hello @kapetr, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a UI bug that prevented agent-generated images from rendering correctly within markdown responses. The fix ensures these images are properly loaded by transforming their internal URIs into API-accessible content URLs, significantly improving the visual presentation of agent interactions.

Highlights

• Image Display Fix: Addresses an issue where agent-generated images were not displayed correctly within markdown responses in the UI.
• URI Rewriting Mechanism: Implements a mechanism to rewrite image URIs that originate from platform files, transforming them to load content through the /api/v1/files/{file_id}/content API endpoint.
• Enhanced URL Transformation: Modifies the urlTransform utility function to intelligently detect and convert platform-specific image URLs, ensuring proper rendering.

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[gemini-code-assist]

Code Review

This pull request correctly fixes an issue with displaying agent-generated images in markdown by transforming their URIs to use the file content API endpoint. The implementation is straightforward and effective. I've included one suggestion to enhance the robustness of the code by handling an edge case where the file ID might be missing from the URI.

[gemini-code-assist]

To improve robustness, it's a good practice to check if a valid fileId is extracted before constructing the content URL. If value is just agentstack://, getFileIdFromFilePlatformUrl would return an empty string, leading to an invalid API call like /api/v1/files//content. Adding a check for fileId ensures we only process valid platform file URLs, falling back to the default transform for invalid ones.

  if (value.startsWith(PLATFORM_FILE_CONTENT_URL_BASE)) {
    const fileId = getFileIdFromFilePlatformUrl(value);

    if (fileId) {
      return getFileContentUrl(fileId);
    }
  }