chore(main): release 0.4.0 (#553)

🤖 I have created a release *beep* *boop*
---


##
[0.4.0](v0.3.14...v0.4.0)
(2025-11-19)


### Features

* Add client-side extension support
([#525](#525))
([9a92bd2](9a92bd2))
* **rest, jsonrpc:** Add client-side extension support
([9a92bd2](9a92bd2))

---
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 +1,13 @@
 # Changelog
 
+## [0.4.0](https://github.com/a2aproject/a2a-python/compare/v0.3.14...v0.4.0) (2025-11-19)
+
+
+### Features
+
+* Add client-side extension support ([#525](https://github.com/a2aproject/a2a-python/issues/525)) ([9a92bd2](https://github.com/a2aproject/a2a-python/commit/9a92bd238e7560b195165ac5f78742981760525e))
+* **rest, jsonrpc:** Add client-side extension support ([9a92bd2](https://github.com/a2aproject/a2a-python/commit/9a92bd238e7560b195165ac5f78742981760525e))
+
 ## [0.3.14](https://github.com/a2aproject/a2a-python/compare/v0.3.13...v0.3.14) (2025-11-17)