/simplify: reuse confirmDoctorFix + take repo in PushMigratedCheckpointRefs
Commit

- doctor migrate-checkpoints now reuses the existing confirmDoctorFix helper instead of a near-duplicate confirm form — picking up its context-cancellation guard (huh opens the TTY during startup regardless of ctx state) and dropping the huh/errors/context imports.
- PushMigratedCheckpointRefs takes the *git.Repository the command already opened rather than re-opening one, matching the strategy entry-point pattern and removing a redundant repo open per invocation.
Co-Authored-By: Claude Opus 4.8 (1M context) noreply@anthropic.com Entire-Checkpoint: 01f324c13852
Checkpoints
Checkpoint 1