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/multi-agent-mux-create/scripts/worktree_prepare.sh

@@ -79,7 +79,7 @@ fi
 if [ "$DRY_RUN" = "1" ]; then
   echo "[dry-run] control root: $MAIN"
   echo "[dry-run] worktree: $WT (branch $BRANCH${BASE_REF:+, base $BASE_REF})"
-  echo "[dry-run] own .venv (from $MAIN/.venv/bin/python + requirements*.txt) and shared info/exclude entries; submodules: $([ "$SUBMODULES" = 1 ] && echo init || echo skipped)"
+  echo "[dry-run] own .venv (from $MAIN/.venv/bin/python + the delegate-job requirements.txt and requirements*.txt) and shared info/exclude entries; submodules: $([ "$SUBMODULES" = 1 ] && echo init || echo skipped)"
   [ -n "$CREATOR_AGENT" ] && echo "[dry-run] creator: $CREATOR_AGENT as $SESSION (role $ROLE)"
   exit 0
 fi
@@ -122,12 +122,16 @@ elif [ -x "$WT/.venv/bin/python" ]; then
 elif [ -x "$MAIN/.venv/bin/python" ]; then
   "$MAIN/.venv/bin/python" -m venv "$WT/.venv" || { echo "ERROR: could not create '$WT/.venv'" >&2; exit 1; }
   req=()
-  for f in requirements.txt requirements-dev.txt; do
+  # the same files deploy/install.sh installs into the control root's venv
+  for f in .agents/skills/multi-agent-mux-delegate-job/requirements.txt requirements.txt requirements-dev.txt; do
     [ -f "$WT/$f" ] && req+=(-r "$WT/$f")
   done
   if [ "${#req[@]}" -gt 0 ]; then
-    "$WT/.venv/bin/python" -m pip install -q "${req[@]}" \
-      || { echo "ERROR: pip install into '$WT/.venv' failed; fix it and re-run (the worktree is kept)" >&2; exit 1; }
+    if ! "$WT/.venv/bin/python" -m pip install -q "${req[@]}"; then
+      rm -rf "$WT/.venv"  # review D1: a half-made venv would be reported as kept by the next run
+      echo "ERROR: pip install into '$WT/.venv' failed (network to the package index is needed); the venv was removed, the worktree is kept - fix it and re-run" >&2
+      exit 1
+    fi
   fi
   VENV_STATE="created"
 else