correlator: address #116 review — call talkgroup id in the prompt, sort candidates

drb-correlation-review: ship, with two bounds the low-bar link rule needs.

1. _call_block emitted only the talkgroup NAME while _inc_summary emits
   numeric tg ids, so the "same talkgroup" precondition in _RULES was
   unevaluable and the low link bar applied unconditionally. _call_block now
   prints "Talkgroup: <name> (id <n>)".
2. ctx["recent"] is an unordered Firestore slice with no order_by; a busy 2h
   window (~40 active incidents) showed the model an arbitrary half of the
   candidates. _prompt_incidents() sorts by updated_at desc before the [:20]
   cap — also makes each row's idle: field monotonic.

+2 tests. Full c2-core suite green (sandboxed venv).

Review follow-ups (not blockers): _parse_response demotes an unresolvable
link to orphan (drops the call) rather than falling back to rules — now on
rising link volume; the 45% tiebreak escalation rate / smart-model cost is
untouched; _ROAD_RE swallows leading tokens so "10 Parker Street" still
won't road-overlap "Parker St".

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

drb-c2-core/tests/test_correlator_115.py

@@ -14,7 +14,7 @@ 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
+from app.internal.llm_correlator import _inc_summary, _prompt_incidents
 
 NOW = datetime(2026, 9, 7, 8, 0, 0, tzinfo=timezone.utc)
 
@@ -52,3 +52,16 @@ 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")
+
+
+def test_prompt_incidents_is_most_recently_active_first_and_capped():
+    recent = [
+        {"incident_id": f"i{n}", "updated_at": f"2026-09-07T0{n}:00:00+00:00"}
+        for n in range(1, 8)
+    ]
+    ordered = _prompt_incidents(recent)
+    assert [i["incident_id"] for i in ordered] == ["i7", "i6", "i5", "i4", "i3", "i2", "i1"]
+    assert len(_prompt_incidents(recent * 5)) == 20
+    # falls back to started_at when updated_at is absent, and never raises
+    assert _prompt_incidents([{"incident_id": "a", "started_at": NOW.isoformat()},
+                              {"incident_id": "b"}])[0]["incident_id"] == "a"