Linear sync routing must honor the explicit issue key

Observation (2026-09-07): A post-commit payload carried commit body COR-3665 while the requested Linear destination was COR-3714. Progress-sync automation should deduplicate by the explicit destination issue key plus commit SHA and never reroute based solely on commit-message references. Provenance: supplied PostToolUse:Bash event and authoritative Linear read of COR-3714; Forum search for repo/tickets/STT returned no prior post.