correlator: give the LLM tier what it needs to link, stop it defaulting to "new" (server-26#115)

The 2026-09-07 measurement window (CORRELATION_REVIEW_0907.md) showed the
consensus tiebreaker was the dominant over-split driver: it ran on 45% of
calls and resolved link/orphan disagreements as "new" ~24/25 of the time,
shattering one Mohegan Park car-alarm job into 9 incidents and opening ~7
incidents from radio checks / roll calls.

Two causes, two fixes:

1. `_inc_summary` gave the model `id|type|loc|units|tags|idle` — no title,
   no talkgroup. It literally could not see that two "car alarms, Mohegan
   Park Ave/Avenue" incidents on TG 9560 were the same. Now includes the
   incident title (the strongest same-event signal) and talkgroup.

2. `_RULES` told the model "orphan when in doubt — conservative is always
   correct". For a system that over-splits, that is backwards: a wrong link
   is cheap, a duplicate incident is the failure. Rewritten to: prefer link
   for a plausible same-talkgroup continuation (low bar), reserve "new" for a
   genuinely different event, and explicitly "orphan" non-incidents (radio
   checks, roll call, 10-8/10-98, mileage logs).

Plus `_extract_road_ids` now canonicalises street-type synonyms
(Avenue→ave, Street→st, Road→rd, ...), so "Mohegan Park Avenue" and
"Mohegan Park Ave" share a road id — that one difference was splitting the
car-alarm incident.

+tests/test_correlator_115.py. Full c2-core suite green (sandboxed venv).
Bigger levers deferred to follow-ups: the consensus escalation itself (should
a cheap-LLM "orphan" ever reach a tiebreak?), a first-class road-overlap fit
signal in _call_fits_incident, geocode coverage.

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

drb-c2-core/tests/test_correlator_115.py

@@ -0,0 +1,54 @@
+"""
+server-26#115 — the tiebreaker manufactured incidents because it was blind to
+what would tell it two incidents are one.
+
+Two low-risk supports for the reframed prompt:
+  1. `_extract_road_ids` collapses street-type synonyms, so "Mohegan Park Ave"
+     and "Mohegan Park Avenue" share a road id (they were splitting one
+     car-alarm incident into two).
+  2. `_inc_summary` now carries the incident title and talkgroup, the two
+     signals the model needs to recognise a same-channel continuation.
+"""
+from datetime import datetime, timezone
+
+from app.internal.incident_correlator import (
+    _extract_road_ids, _location_mentions_road_overlap,
+)
+from app.internal.llm_correlator import _inc_summary
+
+NOW = datetime(2026, 9, 7, 8, 0, 0, tzinfo=timezone.utc)
+
+
+def test_avenue_and_ave_are_the_same_road_id():
+    assert _extract_road_ids("Mohegan Park Avenue") == _extract_road_ids("Mohegan Park Ave")
+    assert _extract_road_ids("191 Broadway Street") == _extract_road_ids("191 Broadway St")
+    assert _extract_road_ids("North State Road") == _extract_road_ids("North State Rd")
+
+
+def test_road_overlap_matches_across_the_synonym():
+    assert _location_mentions_road_overlap("multiple car alarms Mohegan Park Avenue",
+                                           ["patrol to Mohegan Park Ave"]) is True
+    # still discriminates genuinely different streets
+    assert _location_mentions_road_overlap("Oak Avenue", ["Elm Avenue"]) is False
+
+
+def test_inc_summary_carries_title_and_talkgroup():
+    s = _inc_summary({
+        "incident_id": "abc123",
+        "type": "police",
+        "talkgroup_ids": [9560],
+        "title": "Nuisance Alarm at Mohegan Park Ave",
+        "location": "Mohegan Park Ave",
+        "units": ["Headquarters"],
+        "tags": ["car-alarm"],
+        "updated_at": NOW.isoformat(),
+    }, NOW)
+    assert "title:'Nuisance Alarm at Mohegan Park Ave'" in s
+    assert "tg:[9560]" in s
+    assert "id:abc123" in s
+
+
+def test_inc_summary_omits_missing_optional_fields():
+    s = _inc_summary({"incident_id": "x", "updated_at": NOW.isoformat()}, NOW)
+    assert "title:" not in s and "tg:" not in s and "loc:" not in s
+    assert s.startswith("id:x")