refactor(issue-17): item 4 - the delegate-job wrapper's decisions move to Python

The wrapper keeps spawn / wait / kill, key injection and the herdr
diagnostic probe; what it decided in bash is now lib_py/delegation/wrapper.py,
reached through one `_decide` helper:

- finalize_unfinished: the clock choice, the disk grace and broker
  re-observation, the close request / label, the close and the event
  (finalize-begin / finalize-end; bash runs only the busy probe between them)
- start_stall_watch: whether to watch (MAM_STALL_WATCH, remote, human)
- _map_sub_rc, _rc_for (+ MAM_DELEGATE_FAIL_CLOSED), the subscriber
  early-exit check and cmd_wait's rc normalisation
- mam_int / mam_int_knob run lib_py/ints.py, which is also the runner's
  _positive_int: one implementation of the Issue #26 rule

No behaviour change: tests/test_issue17_item4_decisions.py runs the old
bash functions (copied verbatim from 7209750) and the new wrapper on the
same inputs and compares output, FINAL_JOB_STATUS and the registry /
publish calls. Three static tests that pinned the old bash literals now
pin the Python entry points instead.

Refs #17

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

MESSAGING.md

@@ -197,7 +197,7 @@ orchestrator's disk, take part on equal terms.
 | Rule | Contract | Where |
 |---|---|---|
 | **Heartbeat obligation** | While working, the agent publishes `progress` at least every **N** s (`heartbeat_sec`, default 30). `publish_event.py --event started --heartbeat N` starts a detached timer that publishes `progress` (`detail: heartbeat`) every N s with the same `dispatch_token`/`attempt_id`, so the agent does not have to remember. No heartbeat can follow a terminal event: the terminal publish first raises an attempt-scoped barrier (`<registry>/<job>.heartbeat.barrier`, written under the registry lock that also allocates seqs, so a beat either took its seq before it or is refused), then stops the timer through `<registry>/<job>.heartbeat.pid` and waits for it to drain its in-flight beats (killing it after `MAM_HEARTBEAT_DRAIN_S`, default 1 s - a beat still on the wire is cancelled, never allowed to trail the terminal), and only then takes its own seq; replacing the timer (another `started --heartbeat` for the job) drains or kills the previous one the same way before it hands over the pidfile. Starts, replacements and stops of a job's timer are serialized by a per-job lifecycle lock (`<registry>/<job>.heartbeat.lock`, separate from the seq lock): a start that finds the attempt ended arms nothing, an exiting timer never waits for that lock, and a timer whose pid could not be recorded is killed at once. The timer also stops itself on a terminal record or barrier, on re-dispatch, after `timeout_sec`, and within one period of the agent process it watches going away (`--watch-pid`, default the nearest agent-CLI ancestor of the publishing command; a remote runner watches itself) - a crashed agent stops heartbeating, an alive-but-stuck one does not. | `lib_py/delegation/heartbeat.py`, `publish_event.py --heartbeat` |
-| **Unresponsive** | The orchestrator treats a job as unresponsive after **K x N** s without any event (`heartbeat_misses`, default 4 → 120 s; `--idle-timeout` overrides). K x N is when silence is *detected*; the wrapper's post-idle grace below can stretch the final close to about 2 x K x N. The subscriber's idle clock counts every accepted event, and a retained state only when its seq is newer than every event and state already accepted - the same snapshot re-delivered on a reconnect, or an older one, is not liveness; the wrapper's post-idle grace re-reads only the job's events.log (`_recent_disk_heartbeat`, written before every wire publish). herdr status and the pane are logged once as a *diagnostic* (`liveness: ... herdr/pane says busy=yes/no (diagnostic only)`) and never decide. | `multi-agent-mux-delegate-job` (`finalize_unfinished`), `job_subscriber.py` |
+| **Unresponsive** | The orchestrator treats a job as unresponsive after **K x N** s without any event (`heartbeat_misses`, default 4 → 120 s; `--idle-timeout` overrides). K x N is when silence is *detected*; the wrapper's post-idle grace below can stretch the final close to about 2 x K x N. The subscriber's idle clock counts every accepted event, and a retained state only when its seq is newer than every event and state already accepted - the same snapshot re-delivered on a reconnect, or an older one, is not liveness; the wrapper's post-idle grace re-reads only the job's events.log (`recent_disk_heartbeat`, written before every wire publish). herdr status and the pane are logged once as a *diagnostic* (`liveness: ... herdr/pane says busy=yes/no (diagnostic only)`) and never decide. | `multi-agent-mux-delegate-job` (`finalize_unfinished`, decided by `lib_py/delegation/wrapper.py`), `job_subscriber.py` |
 | **Delivery** | After the prompt is handed over (herdr accepted the submission, or the remote dispatch was published), the agent's `started` must arrive within **T** s (`ack_timeout_sec`, default 180; a real agent reads the brief before it runs the start command): the registry leaves `pending`, a `started` line lands in events.log, or the subscriber prints one. No `started` within T → the inject fails closed: rc 1, registry `error` (`agent_blocked`), and the prompt is **never re-injected**. `send_keys_safe` confirms an accepted-but-unconfirmed submission only by `agent_status == working` or the job's `started`; pane changes and busy tokens are no longer signals. | `_wait_started`, `lib.sh: _sks_job_started` |
 | **Termination** | Only `completed` / `error` (and an operator `cancelled`) end a job. Terminal immutability (Issue #6 CAS) refuses anything that arrives after `deadline_timeout` closed the job. | `engine.py` |
 | **Wire durability** | Every event (QoS 1) is followed, on the same connection, by a **retained** `<topic_prefix>/state` message (`event: state`, `status`, `last_event`, `seq`, signed like an event). A subscriber that connects or reconnects receives it at once: a terminal status ends the wait, a state whose seq is newer than every event and state already accepted resets the idle window (a re-delivered or older snapshot still recovers a terminal status but is not liveness), and a `seq` beyond the last one seen is recorded as `seq_gap` in the audit log (also for gaps between events). paho reconnects on its own; `on_connect` re-subscribes both topics and logs `reconnected`. | `publish_event.py: build_state_payload`, `job_subscriber.py: _on_state` |