- Route the transcript-derived shortId through sanitizeSessionId so the
fallback and transcript branches remain byte-for-byte equivalent for any
non-UUID session IDs that still land in CLAUDE_SESSION_ID (greptile P1).
- Clarify the inline comment in the first regression test: clearing
CLAUDE_SESSION_ID exercises the transcript_path branch, not the
getSessionIdShort() fallback (coderabbit P2).
Refs #1494