feat(nws, normalizers): add NWS hourly forecast normalization and enforce canonical float rounding

- Implement full NWS hourly forecast normalizer (raw.nws.hourly.forecast.v1 → weather.forecast.v1)
- Add GeoJSON forecast types and helpers for NWS gridpoint hourly payloads
- Normalize temperatures, winds, humidity, PoP, and infer WMO condition codes from forecast text/icons
- Treat forecast IssuedAt as EffectiveAt for stable, dedupe-friendly event IDs

- Introduce project-wide float rounding at normalization finalization
  - Round all float values in canonical payloads to 2 decimal places
  - Apply consistently across pointers, slices, maps, and nested structs
  - Preserve opaque structs (e.g., time.Time) unchanged

- Add SchemaRawNWSHourlyForecastV1 and align schema matching/comments
- Clean up NWS helper organization and comments
- Update documentation to reflect numeric wire-format and normalization policies

This establishes a complete, deterministic hourly forecast pipeline for NWS
and improves JSON output stability across all canonical weather schemas.

internal/normalizers/common/finalize.go

@@ -14,10 +14,13 @@ import (
 //   - ID/Kind/Source/EmittedAt are preserved by copying the input event.
 //   - EffectiveAt is only overwritten when effectiveAt is non-zero.
 //     If effectiveAt is zero, any existing in.EffectiveAt is preserved.
+//   - Payload floats are rounded to a stable wire-friendly precision (see round.go).
 func Finalize(in event.Event, outSchema string, outPayload any, effectiveAt time.Time) (*event.Event, error) {
 	out := in
 	out.Schema = outSchema
-	out.Payload = outPayload
+
+	// Enforce stable numeric presentation for sinks: round floats in the canonical payload.
+	out.Payload = RoundFloats(outPayload, DefaultFloatPrecision)
 
 	if !effectiveAt.IsZero() {
 		t := effectiveAt.UTC()