docs(breg): note the client geometry break and what a geometry contract change costs

Record the polygon feature and the client geometry type change in the BReg
changelog, with migration steps for Rust, TypeScript and Python. Say in the
spatial queries guide that changing a geometry field's precision, bbox or
maximumPositions is a field type change that needs a reviewed migration, and
what happens when a retained value violates a tightened contract.

Drop a Point validator assertion that pinned a precision-9 refusal of a valid
coordinate; issue #2645 tracks the validator.

BREAKING CHANGE: the geometry of a GeoJSON Feature in the Rust, Node.js and
Python clients is a union of Point, Polygon and MultiPolygon. In Rust, match
BRegGeoJsonGeometry::Point(point) before reading coordinates. In TypeScript,
narrow on geometry.type === "Point". In Python, type checkers see the union.

Signed-off-by: Jeremi Joslin <jeremi@joslin.fr>

Author: jeremi

crates/registry-breg-client/src/actions.rs

@@ -1890,7 +1890,7 @@ mod tests {
     }
 
     #[test]
-    fn polygon_precision_nine_accepts_near_zero_coordinates_without_changing_point() {
+    fn polygon_precision_nine_accepts_near_zero_coordinates() {
         let coordinate = json!(0.000000001);
         assert!(coordinate.to_string().contains('e'));
         assert!(valid_action_input(
@@ -1905,11 +1905,6 @@ mod tests {
             }),
             None,
         ));
-        assert!(!valid_action_input(
-            &json!({"type":"Point","coordinates":[0.000000001,0.000000001]}),
-            &json!({"type":"crs84-point","precision":9}),
-            None,
-        ));
     }
 
     #[test]

products/breg/CHANGELOG.md

@@ -5,6 +5,22 @@
 - `bregctl project-dev` runs BReg projects, including spatial projects, from a
   `breg/project-dev` v1alpha1 plan. It is an alpha format and may change.
   `rstack dev` is its entry point.
+- A `crs84-polygon` field stores a bounded `Polygon` or `MultiPolygon` in
+  WGS 84 longitude and latitude. It takes `precision`, `maximumPositions` and
+  an optional `bbox`, and the compiler validates it with PostGIS and generates
+  a stored geometry column with a GiST index. A bbox grant in an access
+  profile filters Polygon and MultiPolygon fields by bounding-box
+  intersection, as it does for a Point. The GIS profile and the spatial
+  clients carry the new geometry types.
+- BREAKING: The geometry of a GeoJSON Feature in the Rust, Node.js and Python
+  clients is a union of Point, Polygon and MultiPolygon, where it was always
+  a Point. The wire format of a Point is unchanged. In Rust, `geometry` is
+  `Option<BRegGeoJsonGeometry>` instead of `Option<BRegGeoJsonPoint>`; match
+  `BRegGeoJsonGeometry::Point(point)` before reading `coordinates`. In
+  TypeScript, `GeoJsonGeometry` replaces `GeoJsonPoint` on a feature; narrow
+  on `geometry.type === "Point"` before reading `coordinates`. In Python the
+  `.pyi` stubs describe the union, so a type checker flags code that assumes a
+  Point.
 
 ## 0.46.0 - 2026-11-08
 

products/breg/SPATIAL-QUERIES.md

@@ -186,14 +186,25 @@ history or exports. PostGIS types, functions and operators are schema-qualified.
 
 Adding or changing the geometry binding or bbox grant requires the normal
 reviewed successor lifecycle. The compiler derives the projection/index DDL.
-an author does not write dummy SQL to enable spatial storage or bbox.
+An author does not write dummy SQL to enable spatial storage or bbox.
 Missing prerequisites refuse before maintenance begins. An apply failure
 after maintenance begins keeps records unavailable until the existing
 reviewed recovery procedure completes. Removing the last bbox grant removes
 the helper. It also removes a Point's generated projection and index when no
 other bbox grant needs them. A Polygon keeps its generated projection and index.
 Stored data, history and the administrator-owned extension and role remain.
 
+Changing a Point or Polygon field's `precision`, `bbox` or `maximumPositions`
+is a field type change, even when it only loosens the contract. It needs a
+[reviewed migration](../../docs/site/src/content/docs/operate/breg-changes.mdx#write-a-reviewed-migration-descriptor)
+with at least one SQL step, a backup binding and a rehearsal receipt. A
+tightening that a retained value violates is not caught by a pre-check: the
+apply fails on the generated check constraint, the target stays non-ready, and
+[the failed-activation recovery](../../docs/site/src/content/docs/operate/breg-changes.mdx#recover-a-failed-activation)
+applies. Issue
+[#2646](https://github.com/registrystack/registry-stack/issues/2646) proposes
+treating a loosening as a compatible change.
+
 Adding the stored projection can rewrite existing rows, and creating its index
 takes locks and additional disk space. Plan a maintenance window and a tested
 backup/restore path for an existing registry. The small quickstart does not