feat(swarm-worker): dispatch prose swarm slots to ephemeral Muse subagents

- daemon: route non-shell slot tasks to a fresh subagent session on dev/def/muse
  via muse_hybrid; add bin/ to sys.path so muse_hybrid/prompt_envelope import
  under the tmux supervisor
- prompt_envelope: add wrap_subagent_task() - plain task assignment without
  [TOOL tmux/swarm/cron] meta tags (subagents refused those as relayed test traffic)
- box-ctl/reporter: swarm-attach accepts optional session-id, stored as
  slot.subagent_session_id
- executor: _looks_like_shell requires an existing executable (prose like
  'verify ...' no longer misread as shell)
- poller: pick up pending swarms as well as running
- response-harvester: monitor running slot subagent sessions from swarms.json,
  allow '/' in RESULT/VERB job ids, archive ephemeral threads on any verdict
  (OK or FAIL), reap slot sessions for terminal swarms

bin/swarm_worker/reporter.py

@@ -97,6 +97,60 @@ def post_result(swarm_id, slot_index, result_dict, dry_run=False):
                   swarm_id, slot_index, str(resp)[:500])
         return False
 
+def attach_slot(swarm_id, slot_index, agent_id, session_id=None, dry_run=False):
+    """Claim/attach a swarm slot to an agent in box state.
+
+    Args:
+        swarm_id: e.g. "sw-20261005-151307-a222"
+        slot_index: int slot number
+        agent_id: agent string, e.g. "dev"
+        session_id: optional subagent session ID string
+        dry_run: if True, simulate attach without changing state.
+
+    Returns:
+        True on success, False on failure.
+    """
+    if dry_run:
+        print("DRY-RUN would run: %s swarm-attach %s %s %s %s"
+              % (BOX_CTL, swarm_id, slot_index, agent_id, session_id or ""))
+        return True
+
+    cmd = [
+        sys.executable, BOX_CTL, "swarm-attach",
+        str(swarm_id), str(slot_index), str(agent_id),
+    ]
+    if session_id:
+        cmd.append(str(session_id))
+
+    try:
+        proc = subprocess.run(
+            cmd,
+            stdout=subprocess.PIPE, stderr=subprocess.PIPE,
+            timeout=30,
+        )
+    except Exception as e:
+        log.error("attach_slot %s/%s failed to invoke box-ctl: %s",
+                  swarm_id, slot_index, e)
+        return False
+
+    if proc.returncode != 0:
+        err = proc.stderr.decode("utf-8", "replace")[:500]
+        log.error("attach_slot %s/%s box-ctl rc=%d: %s",
+                  swarm_id, slot_index, proc.returncode, err)
+        return False
+
+    try:
+        resp = json.loads(proc.stdout.decode("utf-8", "replace"))
+    except ValueError:
+        log.error("attach_slot %s/%s: box-ctl returned non-JSON output",
+                  swarm_id, slot_index)
+        return False
+
+    if not resp.get("ok"):
+        log.error("attach_slot %s/%s: box-ctl ok=false: %s",
+                  swarm_id, slot_index, str(resp)[:500])
+        return False
+
     return True