Link Ground Zero weather lookup coordinates

Docs/TechnicalDesignDocument.md

@@ -184,6 +184,14 @@ source-backed, generated, validated, packaged, or published tile with center
 coordinates, while placeholder/unknown tiles are skipped. Future source-backed
 tiles therefore become weather-eligible when their registry entries are added.
 
+Ground Zero weather lookup coordinates are explicit in the tile registry. The
+current MVP tile `gz_us_ca_pacifica_utm10n_e544_n4160` uses its tile center,
+latitude `37.5925` and longitude `-122.4995`, as the canonical real-world
+weather lookup point. `Scripts/generate_tile_weather_manifest.py` reads
+`weather_lookup_metadata` when present, falls back to the tile center for
+source-backed tiles, and emits the provider routing used by the weather
+subsystem.
+
 Open-Meteo is the first global MVP weather source. The provider contract is
 stored in `Data/Weather/open_meteo_mvp_source.json`, including the forecast
 endpoint, requested current/daily variables, tile lookup rule, and Agrarian

Docs/Terrain/TileRegistrySchema.md

@@ -78,6 +78,10 @@ Optional growing-zone fields follow the same rule. Crop viability, frost-free
 windows, and growing-season length are generated only for tiles with real source
 work or published packages and explicit growing-zone data.
 
+Optional weather lookup fields are stored only for active/source-backed tiles.
+For MVP, Ground Zero uses its tile-center latitude/longitude as the canonical
+real-world lookup coordinate for live weather and temperature.
+
 ### `terrain_tile_neighbors`
 
 Tracks adjacency for stitching and prefetching.
@@ -136,6 +140,26 @@ Required fields:
 - `data_basis`
 - `generated_at`
 
+### `terrain_tile_weather_lookup_metadata`
+
+Tracks the real-world coordinate and provider routing used to fetch live
+weather and temperature snapshots for a source-backed tile.
+
+Required fields:
+
+- `tile_id`
+- `lookup_latitude`
+- `lookup_longitude`
+- `coordinate_source`
+- `primary_provider`
+- `fallback_provider_eligible`
+- `lookup_rule`
+
+Optional fields:
+
+- `fallback_provider`
+- `generated_at`
+
 ### `terrain_tile_packages`
 
 Tracks generated downloadable packages.