MIME Type Mutation for text Mind assets (txt, yaml, etc. unradable via view_media)

Environment where the instability occurs: Public Mind File encoding: UTF-8 File sizes tested: 500c - 10,000c File content: Plain text with markdown patterns and tabulations

Issue: Text files uploaded as text/plain spontaneously change to application/octet-stream, becoming unreadable by the Mind Assistant.

Evidence: Assets like t0HL57jS2c4NJf and s4gSUmjIKEHhpo flip between readable and unreadable states without user intervention. Files are always UTF-8 encoded .txt files.

Hypotheses:

1. Background re-scanning changes detection post-upload

2. AI moderation system reclassifies files to generic type

3. Silent encoding transformation during storage

4. Cache inconsistency between upload and retrieval services

Impact: Breaks Mind Assistant workflows, forces repeated re-uploads, destroys trust in asset reliability.

Request: Investigate MIME type stability in post-upload pipeline and ensure text/plain persists correctly.