Editing a workout's start date now removes the file at its old month
bucket so the record no longer duplicates on the next reconcile. Seed
reconcile re-checks the tombstone veto before overwriting an upgraded
seed. The watch applies authoritative-empty pushes so remote deletes
prune, and a re-saved finished workout keeps its original end time.
Adds unit tests for the mappers, path bucketing, and status machine.
Claude-Session: https://claude.ai/code/session_01HJDQQDA9QdP8zByg43H5v3
