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/tokens.py

@@ -60,6 +60,34 @@ async def flush_tokens():
     return {"released": len(results)}
 
 
+@router.put("/{token_id}/prefer/{system_id}", status_code=200)
+async def set_preferred_system(token_id: str, system_id: str):
+    """
+    Mark this token as the preferred bot for a system.
+    When a discord_join is issued for any node in that system, this token
+    is tried first before falling back to the general pool.
+    Pass system_id="_none" to clear the preference.
+    """
+    existing = await fstore.doc_get("bot_tokens", token_id)
+    if not existing:
+        raise HTTPException(404, "Token not found.")
+    if system_id == "_none":
+        # Clear any existing preference on the system that pointed to this token.
+        system_doc = await fstore.doc_get("systems", existing.get("preferred_for_system_id", ""))
+        if system_doc:
+            await fstore.doc_set("systems", existing["preferred_for_system_id"], {"preferred_token_id": None})
+        await fstore.doc_set("bot_tokens", token_id, {"preferred_for_system_id": None})
+        return {"ok": True, "preferred_for_system_id": None}
+
+    system_doc = await fstore.doc_get("systems", system_id)
+    if not system_doc:
+        raise HTTPException(404, "System not found.")
+    # Set preference on both sides for easy lookup in either direction.
+    await fstore.doc_set("systems", system_id, {"preferred_token_id": token_id})
+    await fstore.doc_set("bot_tokens", token_id, {"preferred_for_system_id": system_id})
+    return {"ok": True, "preferred_for_system_id": system_id}
+
+
 @router.delete("/{token_id}", status_code=204)
 async def delete_token(token_id: str):
     existing = await fstore.doc_get("bot_tokens", token_id)