chore(main): release 0.3.12 (#538)

🤖 I have created a release *beep* *boop* --- ## [0.3.12](v0.3.11...v0.3.12) (2025-11-12) ### Bug Fixes * **grpc:** Add `extensions` to `Artifact` converters. ([#523](#523)) ([c03129b](c03129b)) --- This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please).

Author: a2a-bot

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Changelog
 
+## [0.3.12](https://github.com/a2aproject/a2a-python/compare/v0.3.11...v0.3.12) (2025-11-12)
+
+
+### Bug Fixes
+
+* **grpc:** Add `extensions` to `Artifact` converters. ([#523](https://github.com/a2aproject/a2a-python/issues/523)) ([c03129b](https://github.com/a2aproject/a2a-python/commit/c03129b99a663ae1f1ae72f20e4ead7807ede941))
+
 ## [0.3.11](https://github.com/a2aproject/a2a-python/compare/v0.3.10...v0.3.11) (2025-11-07)