feat(issue-21): worktree_prepare.sh / worktree_remove.sh (opt-in submodules; judge before any change, single verified --force for submodule worktrees); create starts its reconcile and watchdog from the control root

- worktree_prepare.sh (create skill): idempotent `git worktree add` next to the
  control root (a path inside it is refused), .venv linked to the control
  root's, /.venv and .pytest_cache/ in the shared info/exclude, submodules only
  with --submodules - a failed init removes its own traces (modules/, new
  submodule.* keys in the shared config) and exits 1, since git refuses a plain
  `worktree remove` once modules/ exists - and an optional creator registered
  in the control root's .mam with MAM_NO_SUBSCRIBER_DAEMON=1. Prints BASE= for
  `run_loop.sh --worktree ... --base ... --review-only`.
- worktree_remove.sh (stop skill): every check first, nothing changed on a
  refusal (exit 3): linked and not locked, running sessions only with --stop,
  no open job of those sessions except the delegate jobs stop cancels, clean
  tree including submodules, and inside submodules no modification and no
  commit on no remote (HEAD included - submodules sit on a detached HEAD).
  Then stop, re-check jobs, and remove: plain, or a single --force when the
  worktree holds submodule state.
- lib_py/worktree.py: the parsing behind both (stdlib only).
- A8: create's immediate reconcile and watchdog use the control root's code
  and WORKSPACE_ROOT, not the worktree --workspace's copy.

Tests W1-W6d (local submodules allowed through GIT_CONFIG_* env only).

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

.agents/skills/multi-agent-mux-create/scripts/create_session.sh

@@ -576,8 +576,10 @@ Task: $SUBMIT_JOB_PROMPT"
   
   delegate_publish_event "$DELEGATE_JOB_ID" started "multi-agent-mux session created and instructions injected" "$DELEGATE_JOB_TOKEN" "$DELEGATE_JOB_ATTEMPT"
   # Trigger immediate priority reconcile cycle asynchronously
-  (bash "$WORKSPACE/.agents/skills/multi-agent-mux-monitor/scripts/reconcile.sh" --once >/dev/null 2>&1 &) || true
-  WD_PID=$(start_watchdog "$DELEGATE_JOB_ID" "$WORKSPACE")
+  # Issue #21 phase 2 (A8): the control root's reconcile/watchdog, never the
+  # (unreviewed) copy in a worktree --workspace; identical paths by default.
+  (bash "$SKILL_DIR/multi-agent-mux-monitor/scripts/reconcile.sh" --once >/dev/null 2>&1 &) || true
+  WD_PID=$(start_watchdog "$DELEGATE_JOB_ID" "$WORKSPACE_ROOT")
   echo "watchdog PID: $WD_PID"
 fi
 # Clear cleanup trap as registration was fully successful