correlator: shrink the same-talkgroup escape hatch from 2h to a few minutes (#115)

_recent_incident_on_same_talkgroup previously treated ANY same-talkgroup
incident within the 2-hour correlation_window_hours lookback as 'recent',
which disabled the whole LLM-orphan consensus gate on busy dispatch
channels: window #3 (CORRELATION_REVIEW_0912.md) measured 0/24 gate fires
against the exact target shape (rules=new, llm=orphan, tiebreak=new), with
22/24 explained by a same-talkgroup incident existing somewhere in the
prior 2h — nearly guaranteed on channels producing 3-13 incidents/2h.

Now the escape hatch only counts an incident as recent within
settings.tg_dispatch_thin_idle_minutes (5 min), reusing the same recency
bound the fast/thin path already uses for the 'dispatch, thin ack 10-30s
later' case this hatch exists for, instead of inventing a new constant.

Investigated the 2 unexplained misses (no same-tg incident found even by
a naive full-collection timestamp scan): confirmed ctx["recent"] is built
from status=="active" incidents with over-capacity incidents dropped
(_build_context / _drop_capped), not a full collection scan — an incident
that has auto-resolved or hit incident_max_calls/incident_max_duration
within the window is invisible to this check even though it is
chronologically recent. This does not explain the 2 misses (a same-tg
incident was absent by both checks there, so some other
_call_is_substanceless condition must be responsible), but it is a real
gap in the check as written. Documented in the docstring with a
TODO(server-26#115); fixing it needs a new, non-active-filtered Firestore
query, out of scope for this pass.

Tests: added a regression test proving an incident inside the old 2h
window but outside the new 5-minute window now correctly gates (fails on
main, passes here), plus a test proving a truly recent (<5min) same-tg
incident still escapes the gate as intended. Sandboxed pytest: 327 -> 329
passed (2 new tests), all green.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Tbknwttzou4s46PAykmtix

drb-c2-core/tests/test_consensus_gate.py

@@ -156,10 +156,12 @@ async def test_recent_incident_on_same_talkgroup_is_not_gated():
     ctx = {
         "system_id": "sys-1",
         "talkgroup_id": 9048,
+        "now": NOW,
         "recent": [{
             "incident_id": "inc-live",
             "system_ids": ["sys-1"],
             "talkgroup_ids": ["9048"],
+            "updated_at": (NOW - timedelta(minutes=1)).isoformat(),
         }],
     }
     m_apply, m_tiebreak = await _run_consensus(
@@ -168,6 +170,57 @@ async def test_recent_incident_on_same_talkgroup_is_not_gated():
     m_tiebreak.assert_called_once()
 
 
+# server-26#115 window #3 (CORRELATION_REVIEW_0912.md): the escape hatch used
+# to treat ANY same-talkgroup incident inside the 2h correlation_window_hours
+# as "recent", which on a busy dispatch channel (3-13 incidents/2h) was
+# satisfied almost unconditionally — the gate fired 0/24 times against its own
+# target shape. It now only counts an incident as recent within
+# settings.tg_dispatch_thin_idle_minutes (5 min) — the same bound the
+# fast/thin path uses for the "dispatch, thin ack" case this escape hatch is
+# actually for.
+
+async def test_recent_same_tg_incident_inside_new_short_window_still_escapes_gate():
+    ctx = {
+        "system_id": "sys-1",
+        "talkgroup_id": 9048,
+        "now": NOW,
+        "recent": [{
+            "incident_id": "inc-live",
+            "system_ids": ["sys-1"],
+            "talkgroup_ids": ["9048"],
+            # 3 min ago — inside tg_dispatch_thin_idle_minutes (5).
+            "updated_at": (NOW - timedelta(minutes=3)).isoformat(),
+        }],
+    }
+    m_apply, m_tiebreak = await _run_consensus(
+        _preview("new", {}, ctx=ctx), _llm("orphan"),
+    )
+    m_tiebreak.assert_called_once()
+
+
+async def test_recent_same_tg_incident_older_than_short_window_now_gates():
+    # Regression test for the fix: this incident is well outside the new
+    # 5-minute window but still inside the OLD 2-hour correlation_window_hours
+    # lookback — before the fix this escaped the gate (tiebreak called);
+    # after the fix it no longer counts as "recent", so the gate fires.
+    ctx = {
+        "system_id": "sys-1",
+        "talkgroup_id": 9048,
+        "now": NOW,
+        "recent": [{
+            "incident_id": "inc-stale",
+            "system_ids": ["sys-1"],
+            "talkgroup_ids": ["9048"],
+            "updated_at": (NOW - timedelta(minutes=45)).isoformat(),
+        }],
+    }
+    m_apply, m_tiebreak = await _run_consensus(
+        _preview("new", {}, ctx=ctx), _llm("orphan"),
+    )
+    m_tiebreak.assert_not_called()
+    assert m_apply.call_args[0][0]["decision"]["action"] == "orphan"
+
+
 async def test_recent_incident_on_a_different_talkgroup_still_gates():
     ctx = {
         "system_id": "sys-1",