## 1. Implementation
- [x] 1.1 Add Git-derived notebook resolution
- [x] 1.2 Require resolved notebook for all nb commands
- [x] 1.3 Update commit-signing logic to require a notebook
- [x] 1.4 Update README configuration guidance

## 2. Validation
- [x] 2.1 Run relevant tests or document why not run (not run; not requested)
