The gateway already accepts plain-text config files (.ini, .cfg) and
structured formats (.json, .yaml, .toml) as documents, but not common
source-file extensions. Sending a .ts/.py/.sh file currently requires
renaming it to .txt first.
Adds .ts, .py, .sh as text/plain, consistent with the existing
.ini/.cfg entries.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>