feat: add `spinloop work remove`

[outofcoffee]

Remove a work item from the items file, its record from the state beside it, and its log.

• Takes --items <path> (default ./work.yaml), the same file the orchestrator reads
• A running item cannot be removed: the refusal names it and says to abort it first
• Backlog, done, and failed items are removed from the file, the state, and <file>.logs/<id>.log
• The file must stay parseable after the removal; a running orchestrator picks the change up on its next pass

Part of the work command family with #206, #207, and #208. Builds on #205.

[outofcoffee]

Done in #225