fix(reset): fence every job registry the reset reads, by its physical directory (#78)

Review round 3 R1 (codex): the registration guard chose the workspace marker
from the path's spelling, so a symlink alias of .mam/jobs or a MAM_JOBS_DIR
registry was not refused. The reset now writes .reset-in-progress into each
registry its open-job check reads (.mam/jobs, MAM_JOBS_DIR, a row's other
control_plane.mam_jobs_dir - the latter only for this workspace's sessions),
each under that registry's lock and before the check, and removes it on exit;
register_job reads the marker inside the registry it writes to. The
precheck's separate lock barrier is subsumed by the fence.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.agents/skills/lib_py/delegation/registry.py

@@ -68,12 +68,16 @@ def liveness_window(heartbeat_sec: int, heartbeat_misses: int) -> int:
 
 
 # Issue #78: a reset of a workspace purges its agents' conversations, so no job
-# may be registered in that workspace's .mam/jobs while one runs. The reset
-# publishes .mam/reset-in-progress (pid/lstart, loop_lock.sh's format) and then
-# takes this registry's lock once before it lists the open jobs; the marker is
-# read under the same lock here, so a registration either is written before
-# that listing or sees the marker. The reset's own create (the onboarding job
-# of an agent it recreates) passes the reset's pid in MAM_RESET_OWNER_PID.
+# may be registered for them while it runs. The reset writes RESET_MARKER into
+# every registry its open-job check reads (its own .mam/jobs and MAM_JOBS_DIR,
+# and a row's other control_plane.mam_jobs_dir), each under that registry's
+# lock and before the check: a registration reads it under the same lock, so it
+# is either written before the check or refused - by whatever path it names
+# the directory. The marker carries the reset's pid/lstart (loop_lock.sh's
+# format), its workspace, and for another control plane's registry the
+# sessions it covers. The reset's own create (the onboarding job of an agent
+# it recreates) passes the reset's pid in MAM_RESET_OWNER_PID.
+RESET_MARKER = ".reset-in-progress"
 RESET_OWNER_ENV = "MAM_RESET_OWNER_PID"
 
 
@@ -90,15 +94,13 @@ def _lstart(pid: str) -> str:
     return " ".join(out.split())
 
 
-def reset_refusal(registry_dir: str) -> Optional[str]:
-    """Why a registration in ``registry_dir`` is refused, or None: a live
-    reset of the workspace that owns it (``<ws>/.mam/jobs``) that is not the
-    caller's own. Holder states as loop_lock.sh decides them: a dead or
-    reused pid is stale; ps failing on this process is unknown (refused)."""
-    jobs = os.path.abspath(registry_dir)
-    if os.path.basename(jobs) != "jobs" or os.path.basename(os.path.dirname(jobs)) != ".mam":
-        return None
-    marker = os.path.join(os.path.dirname(jobs), "reset-in-progress")
+def reset_refusal(registry_dir: str, agent_session: str) -> Optional[str]:
+    """Why registering a job for ``agent_session`` in ``registry_dir`` is
+    refused, or None: a live reset fenced this registry (for that session) and
+    the caller is not its own create. Holder states as loop_lock.sh decides
+    them: a dead or reused pid is stale; ps failing on this process is unknown
+    (refused)."""
+    marker = os.path.join(registry_dir, RESET_MARKER)
     try:
         with open(marker, encoding="utf-8") as fh:
             fields = dict(line.split("=", 1) for line in fh.read().splitlines() if "=" in line)
@@ -106,6 +108,8 @@ def reset_refusal(registry_dir: str) -> Optional[str]:
         return None
     except (OSError, ValueError) as exc:
         return "the reset marker %s cannot be read (%s)" % (marker, exc)
+    if "sessions" in fields and agent_session not in fields["sessions"].split(","):
+        return None
     pid = fields.get("pid", "")
     if not pid.isdigit() or os.environ.get(RESET_OWNER_ENV) == pid:
         return None
@@ -115,7 +119,7 @@ def reset_refusal(registry_dir: str) -> Optional[str]:
     if not cur or (fields.get("lstart") and cur != fields["lstart"]):
         return None
     return ("a reset of %s is in progress (pid %s); its agents are being purged and recreated;"
-            " register the job when it has finished" % (os.path.dirname(os.path.dirname(jobs)), pid))
+            " register the job when it has finished" % (fields.get("workspace", "?"), pid))
 
 
 def register_job(
@@ -213,7 +217,7 @@ def register_job(
     if dry_run:
         record["dry_run"] = True
     with registry_lock(registry_dir):
-        refusal = reset_refusal(registry_dir)
+        refusal = reset_refusal(registry_dir, agent_session)
         if refusal:
             raise ResetInProgressError(refusal)
         if mqtt_common._job_path(job_id, registry_dir).exists():