feat(subagent): implement subagent lifecycle tracking and core loop reactive wakeup

- Implement bin/subagent_tracker.py with session registry in subagent-sessions.json
- Register spawned sessions automatically in super-cli.py cmd_deploy
- Add check_subagents() to bin/self_main_loop.py with thread updated watermark comparison
- Add 15-minute stall watchdog with automated parent alerting
- Support 'box subagent spawn' top-level command alias in super-cli.py
- Add symmetrical pip-opm sidechat routing in job-sidechats.json

job-sidechats.json

@@ -111,6 +111,21 @@
     "agent": "pip",
     "description": "pip side of 646-pip coordination pair"
   },
+  "pip-opm": {
+    "thread_uuid": "75feb3a2-be36-499a-b314-bfd5803f1db0",
+    "agent": "pip",
+    "description": "default pip-opm coordination target"
+  },
+  "pip-opm@pip": {
+    "thread_uuid": "75feb3a2-be36-499a-b314-bfd5803f1db0",
+    "agent": "pip",
+    "description": "pip side of pip-opm coordination pair"
+  },
+  "pip-opm@opm": {
+    "thread_uuid": "769955af-21ad-4689-8909-0f75b8f1035c",
+    "agent": "opm",
+    "description": "opm side of pip-opm coordination pair"
+  },
   "pipe-a0d377": {
     "thread_uuid": "cc0aee8f-531a-40af-9e02-27459f57b3ae",
     "agent": "opm",
@@ -130,5 +145,16 @@
     "thread_uuid": "8f9ae8e7-dd3a-46e6-a5ac-3b1bb7cf6d66",
     "agent": "opm",
     "created_at": "2026-10-04T23:19:20.218056+00:00"
+  },
+  "onboarding-test-dev": {
+    "thread_uuid": "f7741827-7b44-45b7-bfb3-c08f8889e93a",
+    "agent": "dev",
+    "created_at": "2026-10-04T23:35:34.711793+00:00"
+  },
+  "onboarding-dev": {
+    "thread_uuid": "31ceab7e-7579-4acc-bcf5-1a10c081aa21",
+    "agent": "dev",
+    "created_at": "2026-10-04T23:37:01+00:00",
+    "note": "onboarding-alpha-probe"
   }
 }