feat(issue-21): persist and forward the control-plane binding in create/resume/stop; status and reconcile honor MAM_JOBS_DIR

A session row now records the control plane it belongs to, and the pane
gets it explicitly instead of relying on env inheritance.

- lib_py/control_plane.py (+ thin lib.sh wrappers mam_control_plane_json /
  mam_control_plane_prefix): the binding is WORKSPACE_ROOT,
  AGENT_SESSIONS_YAML, MAM_JOBS_DIR, DELEGATE_JOB_LOGS_DIR as absolute paths.
- create: the binding is always persisted on the row (`control_plane`) and
  forwarded to the pane only when it differs from what --workspace alone
  implies, as leading K=V tokens that lib.sh's new-session already turns into
  --env (fresh pane) or `env K=V` (reused idle pane). pane.cmd_full and
  start_command stay unprefixed. A binding with whitespace that would have to
  be forwarded is refused with exit 2 (lib.sh splits the flags unquoted); the
  ~/.local/bin wrapper path records the binding but warns it is not forwarded.
- resume: the row's binding wins over the caller's env (a difference is
  reported on stderr) and is forwarded again; a legacy row without one uses
  the caller's binding and update_yaml_resumed.sh records it.
- stop: registry order MAM_JOBS_DIR > the row's mam_jobs_dir >
  $WORKSPACE_ROOT/.mam/jobs > .mam/jobs, exported for delegate_publish_event.
- status: both get_job_status copies look in MAM_JOBS_DIR, the row's
  registry and the matching audit logs before the old candidates.
- reconcile: MAM_JOBS_DIR wins in the subscribe heredoc and is passed in.

Tests T3-0..T3-8 (mock herdr: forwarding is verified at the herdr-call level
only; real pane env propagation is left to item 7). T3-7 is a static guard.

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

.agents/skills/multi-agent-mux-status/scripts/status.sh

@@ -160,7 +160,14 @@ def get_job_status(s):
         return ('-', '-')
 
     project_root = os.environ.get('PROJECT_ROOT', '.')
-    candidates = [
+    # Issue #21: MAM_JOBS_DIR and the registry the row was created against
+    # (control_plane) first, then the matching audit logs, then the old ones.
+    cp = s.get('control_plane') or {}
+    candidates = [os.path.join(r, f"{jid}.json")
+                  for r in (os.environ.get('MAM_JOBS_DIR'), cp.get('mam_jobs_dir')) if r]
+    candidates += [os.path.join(r, jid, 'status.json')
+                   for r in (os.environ.get('DELEGATE_JOB_LOGS_DIR'), cp.get('delegate_job_logs_dir')) if r]
+    candidates += [
         os.path.join('.mam', 'jobs', f"{jid}.json"),
         os.path.join(project_root, '.mam', 'jobs', f"{jid}.json"),
         os.path.join(project_root, '.mam', 'delegate_job_logs', jid, 'status.json'),
@@ -361,7 +368,14 @@ def get_job_status(s):
     project_root = os.environ.get('PROJECT_ROOT', '.')
     # Candidate locations (review item 6: project-root-relative, no hardcoded abs paths):
     #   1) cwd-relative registry  2) project-root registry  3) project-root audit log
-    candidates = [
+    # Issue #21: MAM_JOBS_DIR and the registry the row was created against
+    # (control_plane) first, then the matching audit logs, then the old ones.
+    cp = s.get('control_plane') or {}
+    candidates = [os.path.join(r, f"{jid}.json")
+                  for r in (os.environ.get('MAM_JOBS_DIR'), cp.get('mam_jobs_dir')) if r]
+    candidates += [os.path.join(r, jid, 'status.json')
+                   for r in (os.environ.get('DELEGATE_JOB_LOGS_DIR'), cp.get('delegate_job_logs_dir')) if r]
+    candidates += [
         os.path.join('.mam', 'jobs', f"{jid}.json"),
         os.path.join(project_root, '.mam', 'jobs', f"{jid}.json"),
         os.path.join(project_root, '.mam', 'delegate_job_logs', jid, 'status.json'),