intelligence: a plate read on a patrol channel is a traffic stop

Owner: plate reads should become traffic stops. Held-out replay of 09-21
(server-26#170): Ossining's Post 4 stops were read out only as plates
("Frank David Boy, 4514", "Lincoln, Charlie, Robert, 7-4-0-7") and never
became incidents.

The self-initiated backstop now treats two+ phonetic letters followed by
3-7 digits as a stop — but only when extraction found no other event in
the call (a plate on an MVA, tow or parked-car complaint stays with that
event), and never on MTA/rail/bridge/fire/EMS/DPW talkgroups.

c2-core: 475 pass.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

drb-c2-core/tests/test_clearance_tracking.py

@@ -140,3 +140,17 @@ def test_short_stop_report_opens_a_scene():
             return await intelligence.extract_scenes("c1", "Adam 3 on a stop.", "Ch 1 (Patched with 155.310)")
     scenes = asyncio.run(run())
     assert len(scenes) == 1 and scenes[0]["tags"] == ["traffic-stop"] and scenes[0]["incident_type"] == "police"
+
+
+def test_plate_read_on_a_patrol_channel_is_a_stop():
+    from app.internal.intelligence import _self_initiated_backstop as b
+    ch = "Ossining - Police Dispatch"
+    for t in ("Post 4. 52-62, 3-3. Hemlock Circle. Frank David Boy, 4514. 10-8.",
+              "4, Ossining. 52-22, Ramapo, New York. Lincoln, Charlie, Robert, 7-4-0-7 on a Chevy.",
+              "New York, Mary, Charlie, Nora, 5-8-6-7."):
+        assert b(t, [], None, "routine", ch) == (["traffic-stop"], "police", "minor"), t
+    # a plate on a call that is already about something else stays with it
+    assert b("MVA, plate Mary George Sam 2740", ["mva"], "accident", "moderate", ch) == (["mva"], "accident", "moderate")
+    # not on rail/bridge channels, and not without digits
+    assert b("Frank David Boy 4514", [], None, "routine", "MTA Bridges and Tunnels - Whitestone") == ([], None, "routine")
+    assert b("Charlie, David, go ahead.", [], None, "routine", ch) == ([], None, "routine")