refactor(phase3c): migrate FIRMS fusion broadcasts to formatter+decider (#34)

Migrate the three FIRMS fire-tracker BROADCAST paths (wildfire_growth,
wildfire_spotting, wildfire_halted) behind the registry, NO cutover.
Attribution/pass/centroid/perimeter plumbing stays inline; legacy live
path is byte-identical.

- gating/firms.py decide() discriminates on handler-stamped _kind
  (firms_growth/firms_spotting/firms_halt)
- wildfire_growth reuses formatters/fire.py (verified byte-identical:
  growth SELECT uses current_* columns _render doesn't read, so the wire
  is the movement+anchor line with "size/containment unknown" — a latent
  legacy quirk, reproduced exactly, NOT fixed)
- formatters/firms.py renders spotting + halt wires
- tier-b (flagged): the eager latch writes (fires.last_spotting_broadcast_at,
  fires.halt_broadcast_at) move into deferred commit closures — a dropped
  broadcast no longer burns the latch. Validated by gate-sequence, not
  golden bytes. Not-cutover live path keeps eager latches verbatim.
- FIRMS broadcasts never touch event_log (eager handled=1 at pixel
  storage) → no event_log flip to wrap
- _maybe_emit_cluster stays dead (unconditional return None) + test

Deferred follow-ups (unchanged): env/firms.py native hotspot broadcast
neutralization; native canonical emission.

27 new tests; fire-tracker + firms handler suites preserved; full suite
at 34-failure baseline (1597 passed).

Co-authored-by: Matt Johnson <mj@k7zvx.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

work/tests/test_fire_refactor.py

@@ -310,10 +310,14 @@ class TestRegistration:
 
     @pytest.mark.parametrize(
         "cat", ["wildfire_hotspot", "new_ignition",
-                "unattributed_hotspot_cluster", "wildfire_growth"])
+                "unattributed_hotspot_cluster"])
     def test_firms_categories_not_captured(self, cat):
-        # FIRMS is deferred; its categories must NOT resolve to the fire
-        # formatter/decider via the "fire" toggle family fallback.
+        # These native FIRMS categories remain deferred; they must NOT resolve
+        # to the fire formatter/decider via the "fire" toggle family fallback.
+        # (Phase-3c migrated the FIRMS FUSION categories wildfire_growth /
+        # wildfire_spotting / wildfire_halted — covered in test_firms_refactor.py
+        # — but growth reuses the fire FORMATTER while keeping its OWN firms
+        # DECIDER, so it is intentionally not asserted here.)
         from meshai.notifications.formatters import get_formatter
         from meshai.notifications.gating import get_decider
         assert get_formatter(cat) is not fire_format