chore: release v0.9.0 (#291)

* chore: release v0.9.0

* Add preface to the changelog

---------

Co-authored-by: acp-release-bot[bot] <246668977+acp-release-bot[bot]@users.noreply.github.com>
Co-authored-by: Ben Brandt <[email protected]>

Author: acp-release-bot[bot]

CHANGELOG.md

@@ -1,5 +1,15 @@
 # Changelog
 
+## [0.9.0](https://github.com/agentclientprotocol/agent-client-protocol/compare/v0.8.0...v0.9.0) - 2025-12-01
+
+This release defines the `_meta` properties in the schema as intended and currently used, which is always an object of key/value pairs, with string keys and arbitrary values.
+
+While this is how everyone is using them, it became clear in code generation that the types weren't quite matching up to the expected usage. This should alleviate some extra checks on the implementer side.
+
+### Added
+
+- [**breaking**] Provide clearer schema for \_meta properties ([#290](https://github.com/agentclientprotocol/agent-client-protocol/pull/290))
+
 ## [0.8.0](https://github.com/agentclientprotocol/agent-client-protocol/compare/v0.7.0...v0.8.0) - 2025-11-28
 
 Some follow-up changes from 0.7.0. Most of the changes were in the Rust schema to make things a bit easier to work with.

Cargo.lock

@@ -1,7 +1,7 @@
 [package]
 name = "agent-client-protocol-schema"
 authors = ["Zed <[email protected]>"]
-version = "0.8.0"
+version = "0.9.0"
 edition = "2024"
 license = "Apache-2.0"
 description = "A protocol for standardizing communication between code editors and AI coding agents"