docs: update for simplified MIME detection (v1.5.1)

TODO.md

@@ -12,7 +12,7 @@ Unstructured intake buffer for ideas, issues, and observations. Items here are r
   - Design: compress-then-encrypt only (not compress-only)
   - Compressed data has high entropy → bypasses entropy enforcement
   - Must enforce encryption when compression enabled (CLI-side)
-  - Server detects compression formats via magic bytes (REQUIRE_BINARY)
+  - Server rejects plaintext via REQUIRE_BINARY (UTF-8 detection)
 - ETag support for conditional requests
 - Neovim/Vim plugin for editor integration
 - Webhook notifications for paste events
@@ -53,8 +53,8 @@ Unstructured intake buffer for ideas, issues, and observations. Items here are r
 
 ## External Dependencies
 
-- Consider adding `python-magic` for better MIME detection (currently magic bytes only)
 - cryptography package required for PKI features (optional otherwise)
+- For full MIME detection, consider `filetype` library (currently text/binary only)
 
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