chore(central-ripout 2d-i): relocate the fire engine + renderer out of central/

Moves the last two live files out of the retired-Central folder. central/ is
now EMPTY and deleted entirely (incl. __init__.py).

- fire-fusion engine (ingest_hotspot_pixel + the growth/cluster/spotting
  engine) → env/fire_fusion.py, next to its sole consumer env/firms.py.
- wildfire text renderer (_render + its live helpers) → env/fire_render.py.

THE COUPLING RESOLVED: firms_handler._handle_pass_boundary had a LAZY import
inside a function body — `from meshai.central.wfigs_handler import _render` —
sitting on the live FIRMS fire-growth path. It is now a normal top-of-file
import (`from meshai.env.fire_render import _render`), visible and greppable.

PURE MOVE — no behavior change:
- The parity oracle (test_fire_refactor.py) PASSES UNCHANGED (only its import
  paths updated) — proving the fire wire output is byte-for-byte identical
  before and after. Fire alerts say exactly what they said.
- handle_firms / handle_wfigs (dead entrypoints, only caller was the deleted
  consumer.py) were KEPT and moved rather than dropped — the wording-cleanup
  PR removes them deliberately. "When unsure, keep."
- fire_render.py's geo-helper imports still point at central_normalizer — that
  file's split is a SEPARATE PR; carried the imports along, did not touch it.

Consumers + test import paths rewired. Full suite: 2059 passed, 0 failed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

work/tests/test_firms_handler.py

@@ -10,8 +10,8 @@ Envelope shape sourced from firms-investigation.md sampling (250 envelopes
 """
 import pytest
 
-from meshai.central import firms_handler
-from meshai.central.firms_handler import handle_firms
+from meshai.env import fire_fusion as firms_handler
+from meshai.env.fire_fusion import handle_firms
 from meshai.persistence import close_thread_connection, init_db
 from meshai.persistence import db as persistence_db