fix(issue-21): loop B review follow-up - one verification target per review prompt, dirty submodules refused, identity self-review recorded like any verdict

- review jobs' [워크트리 컨텍스트] points at the [리뷰 identity] path only (B-2);
  remote re-adjudication gets a matching sentence (N-4)
- dirty/untracked submodule content fails the snapshot and makes a round stale,
  regardless of submodule ignore settings (B-R1)
- with --worktree/--base and no reviewer, the creator self-review takes the
  reviewer path: snapshot diff, evidence check, pre-promotion re-check and the
  identity sidecar; NOT PASS still re-reviews without a correction job (B-R2/B-R3)
- snapshot diff failures keep the UNAVAILABLE marker (N-1); prune only when
  worktree remove fails (N-3); the empty per-loop review dir is removed (N-5)
- tests L17-L21, B-2 assertions in L6/L11; SKILL.md env stale note; import order

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017R3Eg7MEpSWnm1oB9ZPP6G

tests/test_issue18_liveness_contract.py

@@ -24,8 +24,8 @@ sandbox); each stays under a minute.
 from __future__ import annotations
 
 import json
-import re
 import os
+import re
 import signal
 import subprocess
 import sys