stops review + provisional LLM closure

Replay of 433b35d (server-26#170): traffic stops now open incidents
("45 Adam" stop, "CM2" stop), but the bridge MVA split 33/56 — one
transmission ("transport complete") was read as scene-resolved at 14:44
and an LLM closure was final, so the rest of the MVA opened a new one.

- LLM closure is now provisional (reopenable), like a timer close: it is
  inferred from a single transmission.
- review of 433b35d: backstop only matches a unit's own "on a stop"
  self-report (bare "car stop" mentions and "pull over" dropped), never on
  MTA/rail/bridge/fire/EMS/DPW talkgroups ("Train 4 holding on the stop"),
  negation looks 5 words back, and <=5-word reports ("Adam 3 on a stop")
  get a minimal scene instead of being skipped before the backstop.

c2-core: 471 pass.

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

drb-c2-core/app/routers/upload.py

@@ -376,6 +376,7 @@ async def _run_extraction_pipeline(
                     "status": "resolved",
                     "resolved_at": clock.now().isoformat(),
                     "resolved_via": "llm_closure",
+                    "reopenable": True,  # provisional, see _extract_and_correlate
                 })
                 await incident_correlator.maybe_resolve_parent(incident_id)
                 logger.info(f"Auto-resolved incident {incident_id} (LLM closure detection)")
@@ -466,6 +467,11 @@ async def _extract_and_correlate(
                 "status": "resolved",
                 "resolved_at": clock.now().isoformat(),
                 "resolved_via": "llm_closure",
+                # One transmission read as "it's over" ("transport complete")
+                # closed the whole 09-22 bridge MVA at 14:44 and its next 56
+                # calls opened a second incident (server-26#170). Inferred from
+                # a single call, so provisional, like a timer close.
+                "reopenable": True,
             })
             await incident_correlator.maybe_resolve_parent(incident_id)
             logger.info(f"Auto-resolved incident {incident_id} (LLM closure detection)")