Implemented operations helper commands for validation, locking, and status

docs/internal/artifacts.md

@@ -16,7 +16,7 @@ Outputs:
 - resolved artifact path + provenance (`ResolvedSessionArtifact`);
 - runtime catalog entries for built-ins and configured artifacts;
 - requirement sets for canonical previous-session inputs.
-- canonical S3 session, run, current, session config, audio, and promoted artifact keys.
+- canonical S3 session, run, current, session config, session locks, audio, and promoted artifact keys.
 
 ## Boundaries
 Owns:
@@ -47,6 +47,7 @@ Does not own:
 ## S3 key helpers
 - session prefix: `{root_prefix}/campaigns/{campaign}/sessions/{session_id}/`
 - session config: `{session_prefix}/session.yml`
+- session lock store: `{session_prefix}/locks.yml`
 - run prefix: `{session_prefix}/runs/{run_id}/`
 - audio prefix: `{session_prefix}/{session.inputs.audio_s3.prefix}`
 - current manifest: `{session_prefix}/current/manifest.json`