docs: add changeset for array-without-items fix

Author: rifkirr23

.changeset/array_without_items_is_list_of_any.md

@@ -0,0 +1,11 @@
+---
+default: patch
+---
+
+# Treat `type: array` without `items` as a list of Any
+
+An array schema with neither `items` nor `prefixItems` is valid in JSON Schema
+2020-12 (OpenAPI 3.1) and means "array of any type". Previously the generator
+failed such schemas with a `PropertyError` ("type array must have items or
+prefixItems defined"), silently skipping the property or `anyOf` branch. It now
+generates a `list[Any]`, equivalent to `items: {}`.