Mobile: uploading images corrupts session with missing media_type

Bug

When using Claude Code via mobile (phone), uploading an image results in the image being sent without the required media_type field in image.source.base64. This permanently corrupts the session — every subsequent message fails with:

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.246.content.2.image.source.base64.media_type: Field required"}}

Steps to reproduce

1. Open Claude Code on mobile (via /remote-control or claude.ai/code session)
2. Upload/attach an image
3. Send a message
4. Every subsequent message in the session fails with the above error

Expected behavior

Either:

• Images should be sent with the correct media_type field, or
• Image upload should be disabled/blocked on mobile if not supported

Impact

• Session is permanently broken — no way to recover without starting a new session
• User loses all conversation context
• The corrupted image payload is baked into conversation history and resent with every new message

Environment

• Claude Code via remote control / claude.ai/code session on mobile