feat: incident correlation overhaul, signal-based auto-resolve, token fixes

Correlator
- Raise fast-path idle gate 30 → 90 min (tg_fast_path_idle_minutes)
- Fix disambiguate always-commits bug: run _call_fits_incident on winner
  before committing; fall through to new-incident creation if it fails
- Add unit-continuity path (path 1.5): matches all_active by shared unit
  IDs with a reassignment guard, bridges calls past the idle gate
- Add tag-based incident_type inference (_TAG_TYPE_HINTS) as GPT fallback,
  rescuing tagged calls that would have been dropped (616 observed orphans)
- Add master/child incident model: _create_master_incident, _demote_to_child,
  _add_child_to_master; new incidents stamped incident_type="master"
- Add cross-system parent detection (_find_cross_system_parent): two-signal
  scoring (road overlap=0.4, embedding≥0.78=0.3, proximity=0.3, threshold=0.5)
  wired into create-if-new path; creates master shell on first cross-system match
- Add maybe_resolve_parent: auto-resolves master when all children close;
  called from upload pipeline (LLM closure) and summarizer stale sweep
- Add signal-based auto-resolve via units_active/units_cleared tracking:
  GPT now extracts cleared_units per scene; _update_incident moves units
  between active/cleared lists and resolves the incident when active empties;
  stored on call doc for re-correlation sweep reuse
- Add _create_incident initialization of units_active/units_cleared fields

Re-correlation sweep
- Add corr_sweep_count + MAX_SWEEP_ATTEMPTS=3: orphans get 3 attempts
  then are tombstoned as corr_path="unlinked", ending the re-sweep loop
  (previously hammering each orphan 29-31 times per shift)

Intelligence extraction
- Add cleared_units to GPT prompt schema and rules
- Extract and propagate cleared_units per scene; merge across scenes;
  store on call doc for re-correlation sweep

Token management
- Fix token release bug: remove release_token call on discord_connected=False
  in MQTT checkin (transient Discord drops were orphaning bots mid-shift)
- Add PUT /tokens/{id}/prefer/{system_id} endpoint: lock a bot token to a
  system; pass _none as system_id to clear; stored bidirectionally on both
  token and system documents
- discord_join handler resolves preferred_token_id from system doc and passes
  system_name in MQTT payload

drb-c2-core/app/routers/nodes.py

@@ -53,12 +53,24 @@ async def send_command(node_id: str, cmd: CommandPayload):
     payload = cmd.model_dump(exclude_none=True)
 
     if cmd.action == "discord_join":
-        preferred = payload.pop("preferred_token_id", None)
+        # Resolve system doc once — used for preferred token and presence name.
+        system_doc = None
+        system_id = node.get("assigned_system_id")
+        if system_id:
+            system_doc = await fstore.doc_get_cached("systems", system_id)
+
+        # Explicit preferred_token_id in the request beats the system-level preference.
+        preferred = payload.pop("preferred_token_id", None) or (system_doc or {}).get("preferred_token_id")
         token = await assign_token(node_id, preferred_token_id=preferred)
         if not token:
             raise HTTPException(503, "No Discord bot tokens available in the pool.")
         payload["token"] = token
 
+        # Pass system name so the bot can set its Discord presence on join.
+        system_name = (system_doc or {}).get("name")
+        if system_name:
+            payload["system_name"] = system_name
+
     elif cmd.action == "discord_leave":
         await release_token(node_id)