Adds a new 'gt commit' command that wraps git commit and automatically
injects agent identity trailers into commit messages:
- Executed-By: agent identity (e.g., beads/crew/dave)
- Rig: the rig name
- Role: crew, polecat, witness, etc.
- Molecule: pinned molecule ID if any
This enables forensic analysis and audit trails for agent-mediated commits.
Supports common git commit flags: -a, --amend, --no-edit, --allow-empty.
Use --no-trailers to skip adding identity trailers.
4b75b15d53