feat(issue-30): a stall watcher that only notifies

lib_py/stall_watch.py runs beside the wrapper's subscriber for a local herdr
job (started after delivery, stopped when the subscriber ends; MAM_STALL_WATCH=0
turns it off). It follows `herdr agent wait` transitions and publishes only
`progress` events through one publisher; it has no path that closes a job.

- blocked: `stalled:blocked <detection line>` once per episode, never answered.
- idle for MAM_STALL_IDLE_S (600) with no background descendants of the agent
  pid (pane process-info + /proc; adapter resident_children and the heartbeat
  timer excluded) and an empty input box: `stalled:idle` and one nudge.
- input box judged from adapter facts measured on herdr 0.9.1 (codex '›',
  grok frame '│', opencode '┃' block + stop pattern); the whole-pane fallback
  is gone. No facts: withheld + `stall_watch:input_check_unavailable` once;
  never empty for 3 x S: `stall_watch:input_never_empty` once.
- herdr failures are not "no event": warning + `stall_watch:herdr_unavailable:
  <code>` (or agent_not_found), backoff, rc 2 after MAM_STALL_HERDR_FAIL_S
  (120); the wrapper prints the watcher's last lines.
- remote and human jobs are skipped with one log line.
- agent_status_reliable is an adapter field; false turns idle judgement off.
- the loop runner relays stalled:/stall_watch: notices once each.
- scoped_env drops a pane-inherited workspace scope for name lookups (#34 rule).

The module sits at the top of lib_py: delegation and loop may not import the
agent adapters (their sibling-import rules). Idle pane captures of the five
CLIs are fixtures; the mock herdr answers process-info in the real shape.

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

.agents/skills/lib_py/agents/__main__.py

@@ -59,11 +59,16 @@ def main():
         print(f"MAM_INPUT_PROMPT={q(adapter.input_prompt or '')}")
         print(f"MAM_INPUT_PLACEHOLDER={q(adapter.input_placeholder or '')}")
         print(f"MAM_INPUT_RULE_PATTERN={q(adapter.input_rule_pattern or '')}")
+        print(f"MAM_INPUT_FRAME_CHARS={q(adapter.input_frame_chars)}")
+        print(f"MAM_INPUT_BLOCK_PREFIX={q(adapter.input_block_prefix or '')}")
+        print(f"MAM_INPUT_STOP_PATTERN={q(adapter.input_stop_pattern or '')}")
         print(f"MAM_READY_TOKENS={q(adapter.ready_tokens)}")
         print(f"MAM_STRONG_READY_TOKENS={q(adapter.strong_ready_tokens)}")
         print(f"MAM_WEAK_READY_TOKENS={q(adapter.weak_ready_tokens)}")
         print(f"MAM_MODAL_TOKENS={q(adapter.modal_tokens or '')}")
         print(f"MAM_STARTUP_DIALOGS={q(json.dumps(adapter.startup_dialogs))}")
+        print(f"MAM_RESIDENT_CHILDREN={q(json.dumps(list(adapter.resident_children)))}")
+        print(f"MAM_AGENT_STATUS_RELIABLE={1 if adapter.agent_status_reliable else 0}")
         print(f"MAM_EXIT_KEY={q(adapter.exit_key)}")
         print(f"MAM_DELEGATE_AGENT_KEY={q(adapter.delegate_agent_key)}")