Announce agent chat in changelog (#280)

Bit late but whatever

---------

Co-authored-by: Howon Lee <[email protected]>

Author: howonlee

docs/changelog.md

@@ -30,6 +30,16 @@ Our reporting capabilities now extend to Bitbucket Cloud! You can now:
 - Track PR review metrics
 - Deliver reports via Email, Slack, Microsoft Teams, or Discord
 
+## April 11 2025
+
+### Agent Chat
+
+```mdx-code-block
+<ProPlanNotice />
+```
+
+We're thrilled to introduce agentic planning on GitHub for CodeRabbit chat as Generally Available for Pro users. This enhancement lets you make more advanced requests that span multiple files. Just add a review or issue comment on any pull request, or issue comment on an issue, issue tagging `@coderabbitai` along with your natural language request for a code change, and the chat will develop a plan for complex modifications. Upon reviewing the plan and getting your consent, CodeRabbit will emit a stacked PR, commit or copyable snippet to your PR or issue for those code changes.
+
 ## April 8, 2025
 
 ### New Static Analysis Tools

docs/guides/agent_chat.md

@@ -65,7 +65,7 @@ Agent chat can be invoked explicitly with the `@coderabbitai plan` command.
 
 CodeRabbit cannot perform further modifications to opened pull requests. From there, it's your turn to checkout the branch and improve it to satisfaction. We believe that this workflow provides a significant headstart to implementing code.
 
-Agentic Chat is currently only available on Github issue, pull request and pull request review comments. Agentic Chat is an early access product currently.
+Agentic Chat is currently only available on Github issue, pull request and pull request review comments.
 
 ### Help and Feedback