CAS is global (not per-thread). The underlying cmdCas* functions
already dropped threadId in #103, but the CLI dispatch layer still
required it from users. Now cleaned up:
- cas get <hash> (was: cas get <thread-id> <hash>)
- cas put <content> (was: cas put <thread-id> <content>)
- cas list (was: cas list <thread-id>)
- cas rm <hash> (was: cas rm <thread-id> <hash>)
- skill.ts develop topic updated to match