feat(harvester,jobs): fast gateway harvesting, parallel thread polling, dynamic sidechat spawning

- Implement muse_hybrid fast gateway in response-harvester.py with ThreadPoolExecutor
- Reduce harvest cycle time from ~1m50s to ~18s; eliminate browser tab-hopping and CDP lock contention
- Add smart active thread filtering in get_monitored_threads to prune dead historical test pipes
- Fix initial watermark ingestion logic so fresh sidechats process first-arrival job responses
- Configure gw_wait window in dm.py (20s on reply:expected) so backend generation is not prematurely severed
- Update box-http-health, box-service-health, box-deep-health to dynamic timestamped sidechats without reuse_key
- Fix heartbeat job to route to dedicated heartbeat channel

jobs/canary-test.json

@@ -1,14 +1,13 @@
 {
-  "agent": "opm",
-  "chain_next": null,
-  "description": "Canary job to test the dispatcher - sends a simple DM",
   "name": "canary-test",
-  "on_failure": "alert",
-  "prompt_template": "This is a canary test from the job dispatcher.\nJob ID: {job_id}\nDate: {date}\n\nPlease reply to confirm you received this.",
+  "description": "Canary job to test sidechat spawning and main chat driving",
+  "agent": "646",
   "schedule": "manual",
+  "timeout": 300,
+  "on_failure": "alert",
   "sidechat": {
     "create": true,
-    "name_template": "canary-test"
+    "name_template": "canary-{datetime}"
   },
-  "timeout": 300
+  "prompt_template": "Canary test running in dedicated sidechat.\nJob ID: {job_id}\nTime: {datetime}\n\nPlease verify and reply with [RESULT {job_id}] OK."
 }