fix(issue-21): PR #29 delta review follow-up - prepare installs the delegate-job requirements, removes a half-made venv on install failure; prompt dirty flag sees untracked files

- worktree_prepare.sh installs the same files deploy/install.sh does
  (.agents/skills/multi-agent-mux-delegate-job/requirements.txt: paho-mqtt,
  PyYAML) plus requirements*.txt. Without paho the loop wrapper, stop_session
  and the subscriber tests fail in the worktree - seen as 4 suite failures
  in a worktree without its own venv, all passing with one.
- review D1: a failed pip install removes the venv it half made, so the next
  run recreates it instead of reporting VENV=kept (test w1c).
- review D3: the [worktree context] block's uncommitted-changes flag uses
  --untracked-files=all like the guards.
- review D2: the create skill doc says the install needs the package index.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VCgu9Fa9iT7TbJUSzdq4Ff

.agents/skills/lib_py/loop/runner.py

@@ -578,7 +578,7 @@ class LoopRunner:
             r = self._git(src, "rev-list", "--count", f"{base}..HEAD")
             if r.returncode == 0 and r.stdout.strip():
                 count = r.stdout.strip()
-        st = self._git(src, "status", "--porcelain")
+        st = self._git(src, "status", "--porcelain", "--untracked-files=all")
         dirty = "알 수 없음" if st.returncode != 0 else ("있음" if st.stdout.strip() else "없음")
         # a remote reviewer (diff-only) cannot reach this host's paths (B6)
         src_line = ("- 소스 경로: (오케스트레이터 호스트 전용 — 원격 리뷰어는 접근할 수 없음)\n" if remote