feat(issue-21): item 5 review identity - per-round snapshot and snapshot diff, detached review worktree (--review-isolation), stale-round re-review, identity records with evidence, pre-promotion re-check; remote reviewers refused or diff-only (--remote-review)

Active with --worktree/--base only; without them prompts, flow and promotion
are unchanged (a loop_id is recorded in the checkpoint either way).

- Every review round is pinned (B3): the source's HEAD and its working state
  as a tree built through a temporary index (the real index/status/refs are
  untouched); a dirty state becomes a ref-less snapshot commit on HEAD
  (committed as mam-loop, not as the user). An untracked nested repository
  cannot be pinned and is refused. identity = (loop_id, base, head, tree).
- Review isolation (B4): a detached review worktree of the snapshot under
  TMPDIR (default), or `--review-isolation env` (the source root with env and
  temp-dir instructions). Failing to open the tree refuses the round - the
  isolation is never lowered silently. Trees are removed after the round and
  on any exit (run() wraps the body; release_guard too).
- The reviewers' diff comes from the snapshot (B13):
  diff_collect.sh takes an optional head commit for a commit-to-commit diff;
  its two-argument form is byte-identical.
- Stale rounds (B7/B8): after the round the source is measured again; if it
  changed, the round's approvals are discarded and the next iteration
  re-reviews without a correction job (last iteration: rc 1). Only the last
  non-stale round's PASSes are promoted.
- Records (B9/B15): review_rounds in the checkpoint with per-reviewer
  transport/evidence, and report-<jid>.identity.json next to each promoted
  report: evidence review-tree | source-tree | diff-only.
- Pre-promotion re-check (B10): a source changed after approval is not
  promoted (rc 1).
- Remote reviewers (B14, Creator challenge 91c81095): they cannot reach this
  host's review tree. Checked before anything is delegated: refused by
  default; `--remote-review diff-only` admits them with the snapshot SHAs and
  diff as their only evidence (no local path in their prompt), and refuses a
  round whose diff is truncated or unavailable.
- run_loop.sh accepts both options (usage identical to the runner's); the
  legacy shell loop refuses them before the lock.

Tests tests/test_issue21_loop_b.py L1-L16 (22).

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

.agents/skills/multi-agent-mux-loop/scripts/run_loop.sh

@@ -35,6 +35,8 @@ PLANNER_SESSION_OVERRIDE=""
 LOOP_WORKTREE=""
 LOOP_BASE=""
 LOOP_REVIEW_ONLY=0
+LOOP_REVIEW_ISOLATION=""
+LOOP_REMOTE_REVIEW=""
 
 # Print usage instructions
 usage() {
@@ -53,6 +55,8 @@ usage() {
   echo "  --worktree <path>      Source worktree for diff/base/head (control plane stays here)"
   echo "  --base <ref>           Pin the review diff base (must be an ancestor of the source HEAD)"
   echo "  --review-only          Skip implementation; review <base>..HEAD (requires --base)"
+  echo "  --review-isolation <v> Review tree with --worktree/--base: worktree (default) or env"
+  echo "  --remote-review <v>    Remote reviewers with --worktree/--base: refuse (default) or diff-only"
   exit 1
 }
 
@@ -92,6 +96,8 @@ while [[ "$#" -gt 0 ]]; do
     --worktree) LOOP_WORKTREE="$2"; shift 2 ;;
     --base) LOOP_BASE="$2"; shift 2 ;;
     --review-only) LOOP_REVIEW_ONLY=1; shift ;;
+    --review-isolation) LOOP_REVIEW_ISOLATION="$2"; shift 2 ;;
+    --remote-review) LOOP_REMOTE_REVIEW="$2"; shift 2 ;;
     -h|--help) usage ;;
     *) echo "Unknown option: $1"; usage ;;
   esac
@@ -117,8 +123,9 @@ fi
 # diffs the checkout it runs in; the worktree/base options are Python-only.
 # Checked before the freeze and the loop lock (log_* are not defined yet).
 if [ "${MAM_LOOP_PY:-1}" = "0" ] && { [ -n "$LOOP_WORKTREE" ] || [ -n "$LOOP_BASE" ] \
-     || [ "$LOOP_REVIEW_ONLY" = "1" ] || [ -n "${MAM_LOOP_WORKTREE:-}" ]; }; then
-  echo "ERROR: --worktree/--base/--review-only require the Python loop (MAM_LOOP_PY=1)" >&2
+     || [ "$LOOP_REVIEW_ONLY" = "1" ] || [ -n "${MAM_LOOP_WORKTREE:-}" ] \
+     || [ -n "$LOOP_REVIEW_ISOLATION" ] || [ -n "$LOOP_REMOTE_REVIEW" ]; }; then
+  echo "ERROR: --worktree/--base/--review-only/--review-isolation/--remote-review require the Python loop (MAM_LOOP_PY=1)" >&2
   exit 1
 fi