fix(issue-18): bind the heartbeat timer to the agent process; scope started to the attempt; ignore re-sent finished dispatches

Review round 1 (claude NOT PASS) corrections:
- B2: the timer now watches a process - `--watch-pid`, or by default the
  nearest agent-CLI ancestor of the publishing command - and stops within
  one period once it is gone, so a crashed agent stops heartbeating and is
  closed after K x N; a remote runner watches itself. Documented as process
  liveness (an alive-but-stuck agent keeps heartbeating).
- R1: `_wait_started` accepts an events.log `started` only when it carries
  the current dispatch token (loop jobs share one events.log).
- R2: the remote runner ignores a re-sent dispatch of an attempt that
  already reached its terminal.
- R3: registry.md EOF blank line (git diff --check clean).
- R4: the ack error states the effective budget when the wall clock cut it.
- P3: stop_timer verifies the pidfile pid is this job's timer before
  signalling; a retained state message keeps its own seq watermark so it
  can never make the monotonic guard drop its own event.
- MULTI_AGENT_RULES.md timeout section updated for the contract.
- tests: agent-process death stops the timer, recycled-pid safety,
  attempt-scoped started, re-sent dispatch; acceptance 3 now kills the
  agent process instead of the timer. Help captures refreshed
  (--watch-pid). The wrapper can be sourced with
  MAM_DELEGATE_JOB_NO_MAIN=1 for helper-level tests.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VCgu9Fa9iT7TbJUSzdq4Ff

.agents/skills/lib_py/delegation/remote.py

@@ -153,7 +153,7 @@ def clear_dispatch(config, topic: str) -> None:
 # remote side
 # ---------------------------------------------------------------------------
 
-def mirror_job(d: Dict[str, Any], registry_dir: str, session: str) -> str:
+def mirror_job(d: Dict[str, Any], registry_dir: str, session: str) -> Optional[str]:
     """Create the local job record a remote agent publishes against.
 
     The record carries the orchestrator's job_id, auth_token, dispatch_token
@@ -165,8 +165,9 @@ def mirror_job(d: Dict[str, Any], registry_dir: str, session: str) -> str:
     path = mqtt_common._job_path(jid, registry_dir)
     if path.exists():
         old = load_job(jid, registry_dir)
-        if (old.get("dispatch_token") == d.get("dispatch_token")
-                and old.get("status") not in ("completed", "error", "cancelled")):
+        if old.get("dispatch_token") == d.get("dispatch_token"):
+            if old.get("status") in ("completed", "error", "cancelled"):
+                return None  # this attempt already ran to its end: a re-sent dispatch is not run again
             return jid  # same attempt, already mirrored (duplicate delivery)
         with mqtt_common.registry_lock(registry_dir):
             path.unlink()
@@ -206,7 +207,8 @@ def _publish(jid: str, registry_dir: str, event: str, detail: str, d: Dict[str,
     if d.get("attempt_id") is not None:
         argv += ["--attempt-id", str(d["attempt_id"])]
     if heartbeat:
-        argv += ["--heartbeat", str(heartbeat)]
+        # The runner publishes in-process, so the timer must die with the runner.
+        argv += ["--heartbeat", str(heartbeat), "--watch-pid", str(os.getpid())]
     return publish_event.main(argv)
 
 
@@ -214,6 +216,10 @@ def handle_dispatch(d: Dict[str, Any], registry_dir: str, session: str,
                     exec_cmd: Optional[str], python: Optional[str] = None) -> int:
     """Run one dispatched job to its terminal event. Returns the agent rc."""
     jid = mirror_job(d, registry_dir, session)
+    if jid is None:
+        logger.info("dispatch for %s attempt %s already finished here; ignoring the re-sent copy",
+                    d.get("job_id"), d.get("attempt_id"))
+        return 0
     heartbeat = int(d.get("heartbeat_sec") or registry.DEFAULT_HEARTBEAT_SEC)
     rc_started = _publish(jid, registry_dir, "started", "remote runner {} claimed the job".format(session),
                           d, heartbeat=heartbeat)