[Bug] Unhandled API Error when Read tool processes non-image files with image extensions

Bug Description
Summary: Claude Code crashes with "Could not process image" when Read tool is given an HTML file disguised as an image

Steps to reproduce:

1. Download a URL that returns HTML (e.g., an auth-protected image URL that returns login page)
2. Save it as a .png file
3. Use the Read tool to view the "image"
4. Claude Code crashes instead of handling the API 400 error gracefully

Error message:
API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"Could not process image"},"request_id":"req_011CWhVUp5ztioeseSNBCtHD"}

Expected behavior:
Claude Code should catch the API error and display a user-friendly message like "File is not a valid image" rather than crashing.

Context:

• Occurred when /linear-image skill tried to view a Marker.io image that required authentication
• Marker.io returned HTML login page instead of the actual image
• File was saved as .png but contained HTML content
• Claude Code version: 2.0.76
• Session: 5baf32ee-0ade-498b-a275-98f0d64a5cce

Environment Info

• Platform: darwin
• Terminal: iTerm.app
• Version: 2.0.76
• Feedback ID: f07e894b-ec84-4313-b098-58f2879da820

Errors

[{"error":"Error: NON-FATAL: Lock acquisition failed for /Users/bfeld/.local/share/claude/versions/2.0.76 (expected in multi-process scenarios)\n    at XZR (/$bunfs/root/claude:2430:2165)\n    at fUA (/$bunfs/root/claude:2430:1885)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-01-01T23:06:20.888Z"}]