feat(environment): register env signals and wire weather into correlation discovery

Register the seven environmental-exposure signals through the signal registry
as a new "environment" kind (correlation-eligible; off Coach/MCP/FHIR in v1),
and fold their daily series into the correlation engine as lagged behaviour
channels. Weather/daylight now pair against mood, sleep, and vitals through
the existing FDR / effect-size / shrinkage gates, so a thin series degrades to
absent rather than a spurious link. All env channels share one ENVIRONMENT
family so two same-day fields never lag-correlate against each other.

src/components/insights/mood/mood-discovered-relations.tsx

@@ -52,6 +52,15 @@ const CHANNEL_LABEL_KEY: Record<string, string> = {
   HEART_RATE_VARIABILITY: "measurements.typeHeartRateVariability",
   RESTING_HEART_RATE: "measurements.typeRestingHeartRate",
   WEIGHT: "measurements.typeWeight",
+  // v1.25 (W-ENV) — environmental-exposure channels, so a "daylight → mood"
+  // relation reads with its descriptive label instead of the raw ENV_ key.
+  ENV_TEMP_MEAN: "environment.fields.tempMean",
+  ENV_TEMP_MIN: "environment.fields.tempMin",
+  ENV_SUNSHINE: "environment.fields.sunshine",
+  ENV_DAYLIGHT: "environment.fields.daylight",
+  ENV_PRECIP: "environment.fields.precip",
+  ENV_PRESSURE_MEAN: "environment.fields.pressureMean",
+  ENV_PRESSURE_DELTA: "environment.fields.pressureDelta",
 };
 
 /** Keep only the discovered pairs that involve the mood channel. */