chore(central-ripout 2c): relocate gauge sites to env/gauge_sites.py (#163)

Moves the last non-fire live file out of central/. idaho_gauge_sites.py held
USGS stream-gauge site data + threshold ranking — pure hydro/gauge domain,
misfiled among the retired Central handlers.

Applied the owner's rule with a clean split:
- THRESHOLD_RANK (a 5-element list used ONLY by notifications/gating/hydro.py)
  inlined there — single consumer, belongs next to its use.
- The gauge-site lookup (used by env/usgs.py + persistence/curation.py) moved
  to env/gauge_sites.py, next to the usgs adapter that produces gauge data.
- Dropped the redundant "idaho_" prefix (the Idaho scoping is data, not code).

Consumers rewired: env/usgs.py, notifications/gating/hydro.py, and tests.
central/ is now down to firms_handler.py + wfigs_handler.py (the fire pair,
whose relocation is a separate PR because of their cross-file coupling).

Move + import-rewire only, no behavior change. Suite: 2059 passed, 0 failed.

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

work/meshai/central/__init__.py

@@ -2,7 +2,7 @@
 JetStream firehose and normalized it into meshai pipeline Events. The NATS
 consumer is retired (Central is gone); this package now only holds the
 split-file modules still used by the native adapter paths (firms_handler,
-wfigs_handler _render, idaho_gauge_sites). The satellite pieces
-(satpass_handler, tle_handler, pass_predictor) have moved to
-meshai.env.satellite — they're feed-adapter support code, not consumer
-leftovers."""
+wfigs_handler _render). The satellite pieces (satpass_handler, tle_handler,
+pass_predictor) have moved to meshai.env.satellite, and the gauge-site
+lookups have moved to meshai.env.gauge_sites — they're feed-adapter support
+code, not consumer leftovers."""

work/meshai/env/gauge_sites.py

@@ -1,4 +1,4 @@
-"""v0.6-4 Idaho gauge-site lookups (now backed by gauge_sites table).
+"""v0.6-4 gauge-site lookups (now backed by gauge_sites table).
 
 The IDAHO_CURATED_SITES Python dict was migrated to the gauge_sites SQLite
 table in v8.sql. seed_gauge_sites() (called from init_db on first boot)
@@ -6,18 +6,19 @@ populates the table with the original 9 sites. The lookup helpers below
 read from the table via meshai.persistence.curation.
 
 Module exports retained for backward-compat with existing tests:
-    lookup_site, normalize_site_id, THRESHOLD_RANK, compute_threshold_state.
+    lookup_site, normalize_site_id, compute_threshold_state.
 The IDAHO_CURATED_SITES name itself is gone -- new code should call
 lookup_site() (DB-backed) or the curation accessor directly.
+
+(Relocated from meshai/central/idaho_gauge_sites.py -- Central is gone;
+this is pure hydro/gauge domain code, not a Central handler. The "idaho_"
+prefix was dropped on the move: the data is Idaho-scoped but the code
+itself is generic gauge/threshold logic. THRESHOLD_RANK, formerly exported
+here, was inlined into its sole consumer, meshai.notifications.gating.hydro.)
 """
 from typing import Optional
 
 
-# Ordered list of threshold names from low to high. Used to compare
-# "is current threshold higher than prior" (upward crossing detection).
-THRESHOLD_RANK = ["normal", "action", "flood_minor", "flood_moderate", "flood_major"]
-
-
 def normalize_site_id(raw: Optional[str]) -> Optional[str]:
     """Accept 'USGS-13139510', 'USGS:13139510', '13139510', etc. Return the
     canonical 'USGS-<id>' form so the curation table lookups succeed."""

work/meshai/env/usgs.py

@@ -39,11 +39,11 @@ def _cfg_str(config, attr: str, default: str) -> str:
 
 # Maps the flood_status strings _fetch() sets (see severity-classification
 # block above) onto the ranked threshold_state vocabulary the shared hydro
-# gating/formatter modules speak (meshai.central.idaho_gauge_sites.
-# THRESHOLD_RANK / meshai.notifications.gating.hydro / formatters.hydro).
-# Kept local rather than importing from central.idaho_gauge_sites so this
-# adapter has no dependency on the (Central-only, reference-only) central
-# package -- only the string vocabulary is shared, not the code.
+# gating/formatter modules speak (meshai.notifications.gating.hydro.
+# THRESHOLD_RANK / formatters.hydro).
+# Kept local rather than importing from gating.hydro so this adapter has
+# no dependency on the gating package -- only the string vocabulary is
+# shared, not the code.
 _FLOOD_STATUS_TO_THRESHOLD_STATE = {
     "Action Stage": "action",
     "Minor Flood": "flood_minor",

work/meshai/notifications/gating/hydro.py

@@ -74,12 +74,17 @@ import logging
 from typing import Optional
 
 from meshai.adapter_config import adapter_config
-from meshai.central.idaho_gauge_sites import THRESHOLD_RANK
 from meshai.notifications.gating.base import GateResult
 from meshai.persistence import get_db
 
 logger = logging.getLogger(__name__)
 
+# Ordered list of threshold names from low to high. Used to compare
+# "is current threshold higher than prior" (upward crossing detection).
+# Formerly meshai.central.idaho_gauge_sites.THRESHOLD_RANK -- inlined here
+# since this decider was its only consumer.
+THRESHOLD_RANK = ["normal", "action", "flood_minor", "flood_moderate", "flood_major"]
+
 
 def _rank(state: Optional[str]) -> int:
     """THRESHOLD_RANK index for *state*, treating unknown as 0 (normal)."""

work/tests/test_hydro_refactor.py

@@ -208,8 +208,8 @@ class TestGateSequenceParity:
 
     def _canonical(self, fixture):
         """Build canonical data from a Central-style fixture (as the deleted
-        handler used to) via the still-live idaho_gauge_sites helpers."""
-        from meshai.central.idaho_gauge_sites import (
+        handler used to) via the still-live gauge_sites helpers."""
+        from meshai.env.gauge_sites import (
             compute_threshold_state, lookup_site, normalize_site_id,
         )
         env = fixture["envelope"]