feat(central): v0.5.4 -- region-aware subscriptions using Central v0.9.20 regional subjects

Pre-v0.5.4 every Central subscription used a bare wildcard (central.wx.>,
central.fire.>, central.traffic.>, central.quake.>, central.hydro.>,
central.space.>), so a Magic Valley operator flipping nws -> central was
in fact subscribing to the all-US firehose and discarding 95% of events
locally. Central v0.9.20 (2026-05-28) added per-region subject suffixes
so the firehose can be filtered server-side. This wires meshai to use them.

Backend (meshai/central/consumer.py):
- New _subjects_for(adapter, region) replaces the static ADAPTER_SUBJECTS
  dict. ADAPTER_SUBJECTS is retained as an alias to _SUBJECTS_BARE for any
  legacy importers; the dispatcher path is unchanged.
- Per-adapter subject patterns (region='us.id' default):
    nws        -> central.wx.alert.us.id.>     (region BEFORE wildcard)
    usgs_quake -> central.quake.event.>.us.id  (region AFTER wildcard)
    firms      -> central.fire.hotspot.>.us.id
    fires      -> central.fire.incident.id.>   (state token at fixed depth)
                  central.fire.perimeter.id.>
    traffic    -> central.traffic.>.id          (bare state, no us. prefix)
    roads511   -> central.traffic.>.id          (shared with traffic, sub-adapter routing)
    usgs       -> central.hydro.>.us.id
                  central.hydro.>.unknown      (workaround until v0.9.20.1)
    swpc       -> central.space.>               (planetary; region ignored)
- Empty/None region falls back to bare wildcards (pre-v0.9.20 behaviour).
- _subject_owned() pulls region from env.central.region and routes through
  _subjects_for; v0.5.3 sub-adapter routing (owned-sources set) still
  applies on shared subjects like central.traffic.>.id.
- start() logs the active region at connect-time for ops visibility.

Config (meshai/config.py):
- CentralConsumerConfig.region: str = "us.id". One region per consumer
  applies to every central-flipped adapter; per-adapter overrides can
  land in v0.6 when there is a real use case.

Frontend (dashboard-frontend/src/pages/Environment.tsx):
- Central Connection panel gets a Region text input next to URL/Durable.
- EnvConfig.central type extended with region: string.
- Static bundle rebuilt; index-DCFmSeOM.js -> index-B24tHcYj.js.

Tests:
- tests/test_central_region_routing.py (new, 9 cases): asserts the exact
  v0.9.20 subject string for each adapter at region='us.id', the SWPC
  global-stays-global rule, the USGS .unknown workaround, the empty-region
  backward-compat fallback for all 8 adapters, and integration through
  CentralConsumer._subject_owned() with the default region.
- tests/test_central_consumer.py + tests/test_central_sub_adapter_routing.py:
  the two tests that asserted bare-wildcard subjects now set
  env.central.region = "" explicitly to preserve their original concern
  (no region semantics — backward-compat path only).

Why swpc stays global: space weather is planetary -- a CME is detected on
the sun, the geomagnetic response is hemispheric. There is no Idaho-only
solar event; subscribing per-region would only drop events we want.

Why hydro has the .unknown workaround: Central v0.9.20 leaves gauges
whose USGS state can't be inferred on central.hydro.>.unknown. Until
v0.9.20.1 backfills the state tag we subscribe to both filters to
avoid silently losing those rows. Idaho downstream-filtering on
data['_enriched']['usgs_site']['state'] is future v0.6 work.

Orthogonal to v0.5.2 dispatcher guards (staleness / cooldown / dedup)
and v0.5.3 sub-adapter routing: the region filter operates at the NATS
subscription layer (server-side), upstream of everything else.

Verified: pytest 327 passed (318 prior + 9 new region-routing tests);
py_compile clean; frontend build clean. Safe-mode preserved -- no toggle
enabled, no master enabled, no central enabled.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

dashboard-frontend/src/pages/Environment.tsx

@@ -27,7 +27,7 @@ interface EnvConfig {
   traffic: { enabled: boolean; tick_seconds: number; api_key: string; corridors: { name: string; lat: number; lon: number }[]; feed_source?: FeedSource }
   roads511: { enabled: boolean; tick_seconds: number; api_key: string; base_url: string; endpoints: string[]; bbox: number[]; feed_source?: FeedSource }
   firms: { enabled: boolean; tick_seconds: number; map_key: string; source: string; bbox: number[]; day_range: number; confidence_min: string; proximity_km: number; feed_source?: FeedSource }
-  central?: { enabled: boolean; url: string; durable: string }
+  central?: { enabled: boolean; url: string; durable: string; region: string }
 }
 
 type FeedHealth = EnvStatus['feeds'][number]
@@ -406,6 +406,10 @@ export default function Environment() {
             <TextInput label="Durable" value={env.central.durable || ''}
                        onChange={(v) => up({ central: { ...env.central!, durable: v } })}
                        placeholder="meshai-v04" />
+            <TextInput label="Region" value={env.central.region || ''}
+                       onChange={(v) => up({ central: { ...env.central!, region: v } })}
+                       placeholder="us.id"
+                       helper="Central v0.9.20 region token (dotted, e.g. 'us.id'). Empty = bare wildcards (all-US firehose)." />
           </div>
         </div>
       )}