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/publish_event.py

@@ -297,6 +297,9 @@ def main(argv=None) -> int:
                              "(Issue #18; not with a terminal event)")
     parser.add_argument("--no-state", action="store_true",
                         help="do not publish the retained <topic_prefix>/state message")
+    parser.add_argument("--watch-pid", type=int, default=None,
+                        help="bind the heartbeat timer to this process (default: the nearest "
+                             "agent-CLI ancestor; 0 = no watch)")
     parser.add_argument("-v", "--verbose", action="store_true")
     args = parser.parse_args(argv)
 
@@ -456,7 +459,8 @@ def main(argv=None) -> int:
             hb_attempt = hb_attempt if hb_attempt is not None else rec.get("attempt_id", rec.get("iteration", 1))
         try:
             pid = heartbeat_timer.start_timer(job_id, args.registry_dir, args.heartbeat,
-                                              dispatch_token=hb_token, attempt_id=hb_attempt)
+                                              dispatch_token=hb_token, attempt_id=hb_attempt,
+                                              watch_pid=args.watch_pid)
             logger.info("heartbeat timer started (pid %d, every %ss)", pid, args.heartbeat)
         except OSError as exc:
             logger.error("could not start the heartbeat timer: %s", exc)