Let C2 name a talkgroup it already knows

84 of the 100 incidents in the 2026-08-23 dump were titled "Ems — TGID 9048"
or "Other — TGID 9600" -- the fallback, not a description. The title is the
incident's name everywhere it appears: list rows, map pins, Discord alerts.

_create_incident builds it from a content tag and a talkgroup label, and the
label was collapsing to "TGID {id}" because talkgroup_name arrived as None.
It is a plain form field on /upload, forwarded untouched into correlation, and
the node only sends it when OP25 had the name in its loaded tags file -- which
is exactly the case C2 can cover from its own systems collection, where all 125
talkgroup definitions live.

The lookup already existed, on the other path: mqtt_handler resolved it from
the system config on call_start. So the call document held the right name while
the pipeline that titles the incident ignored it. That asymmetry is the bug.

internal/talkgroups.py is now the one implementation -- caller's hint, then the
call document, then the system config -- and both paths use it.
_run_intelligence_pipeline resolves once at the funnel /upload and
/calls/{id}/reprocess share, so the dispatch-channel test, scene extraction and
the title all see a real name. When the call document was the thing missing it,
the resolved name is written back, so the archive and the orphan panel stop
showing a bare TGID too.

Also gives fast/thin a corr_fit_signal. It is 63% of all links and was the only
path writing none, so corr_fit_signal was absent on 295 of 309 calls and the
admin debug view's distribution panel read empty -- looking broken when it was
faithfully reporting that the dominant path records nothing. It now says
thin_recency, which is what actually decided it.

Closes server-26#34. Refs server-26#35 -- the tier's 3.5% invocation rate is a
cost/benefit question, not a bug, and stays open.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

drb-c2-core/app/internal/mqtt_handler.py

@@ -6,6 +6,7 @@ import paho.mqtt.client as mqtt
 from app.config import settings
 from app.internal.logger import logger
 from app.internal import firestore as fstore
+from app.internal import talkgroups
 from app.internal.tenancy import FOUNDING_ORG_ID
 
 
@@ -219,16 +220,12 @@ class MQTTHandler:
             else datetime.now(timezone.utc)
         )
 
-        # Prefer the name from OP25 metadata; fall back to the system config
-        tgid_name = payload.get("tgid_name") or ""
-        if not tgid_name and system_id and payload.get("tgid"):
-            system_doc = await fstore.doc_get_cached("systems", system_id)
-            if system_doc:
-                tgid_int = int(payload["tgid"])
-                for tg in system_doc.get("config", {}).get("talkgroups", []):
-                    if int(tg.get("id", -1)) == tgid_int:
-                        tgid_name = tg.get("name", "")
-                        break
+        # Prefer the name from OP25 metadata; fall back to the system config.
+        # The lookup lives in internal/talkgroups.py because /upload needs the
+        # identical resolution and used to go without it — see server-26#34.
+        tgid_name = await talkgroups.resolve(
+            system_id, payload.get("tgid"), hint=payload.get("tgid_name") or None
+        ) or ""
 
         doc = {
             "call_id": call_id,