docs(fields): teach the spec's { lat, lng } as the stored location value

content/docs/fields/location.mdx

@@ -37,9 +37,10 @@ const officeLocation: LocationFieldMetadata = {
 ```
 
 The coordinates themselves are the field's **value**, not metadata: the widget stores
-an object carrying a `latitude` and a `longitude` and displays it as a comma-separated
-pair. No exported type declares that value shape today, which is tracked as
-[objectui#6154](https://github.com/objectstack-ai/objectui/issues/6154).
+an object carrying a `lat` and an `lng` and displays it as a comma-separated pair.
+That value shape is exported as `LocationValue` by `@objectstack/spec/data` —
+`{ lat, lng, altitude?, accuracy? }` — and it is what
+`valueSchemaFor({ type: 'location' })` validates a stored location against.
 
 The value being edited, and the `className` / `disabled` a host supplies, are **not**
 metadata keys — they are runtime widget props. See [Field Widget Props](/docs/fields/widget-props).
@@ -50,18 +51,25 @@ The location field stores coordinates as an object:
 
 ```plaintext
 {
-  latitude: 37.7749,
-  longitude: -122.4194
+  lat: 37.7749,
+  lng: -122.4194
 }
 ```
 
-Input format: `latitude, longitude`
+`altitude` and `accuracy` are optional numbers on the same object.
+
+**Note**: the stored keys are `lat` and `lng`. The older `{ latitude, longitude }`
+spelling is deprecated and is **rejected** by `valueSchemaFor({ type: 'location' })`
+with `invalid_type` at `[lat]` and `[lng]` — do not author it.
+
+Input format: `latitude, longitude` — a user still types a comma-separated
+latitude-then-longitude pair; only the stored key names are `lat` / `lng`.
 - Example: `37.7749, -122.4194`
 
 ## Coordinate Ranges
 
-- **Latitude**: -90 to 90 (negative = South, positive = North)
-- **Longitude**: -180 to 180 (negative = West, positive = East)
+- **Latitude** (`lat`): -90 to 90 (negative = South, positive = North)
+- **Longitude** (`lng`): -180 to 180 (negative = West, positive = East)
 
 Examples:
 - New York: `40.7128, -74.0060`
@@ -113,7 +121,7 @@ the renderer:
   "type": "object-map",          // the registered type name — there is no `plugin:map`
   "objectName": "store",         // the records to plot
   "map": {                       // the declared config input; markers are derived from the data
-    "locationField": "location", // this page's field, read as { latitude, longitude }
+    "locationField": "location", // this page's field, read as { lat, lng }
     "titleField": "name",        // field used as the marker label
     "zoom": 12,                  // initial zoom level
     // Initial centre as [latitude, longitude]. Used only when no record
@@ -131,11 +139,11 @@ The field validates coordinate ranges:
 
 ```plaintext
 // Valid coordinates
-{ latitude: 37.7749, longitude: -122.4194 } ✓
+{ lat: 37.7749, lng: -122.4194 } ✓
 
 // Invalid - latitude out of range
-{ latitude: 95, longitude: -122.4194 } ✗
+{ lat: 95, lng: -122.4194 } ✗
 
 // Invalid - longitude out of range
-{ latitude: 37.7749, longitude: 200 } ✗
+{ lat: 37.7749, lng: 200 } ✗
 ```