security: remove leaked HF token session file, add session-*.md to gitignore

Removes session-ses_37b6.md from tracking (contained plaintext HuggingFace
API token). Adds session-*.md to .gitignore to prevent future leaks.

NOTE: Token must still be revoked at huggingface.co/settings/tokens.
The token remains in git history and should be scrubbed with git filter-repo.

Closes #52

Co-Authored-By: Terraphim AI <noreply@terraphim.ai>

Author: AlexMikhalev

.gitignore

@@ -46,6 +46,9 @@ data/umls/
 *.pt
 *.pth
 
+# Session files (may contain secrets/tokens)
+session-*.md
+
 # Environment
 .env
 .env.local