docs: describe the Action as commit policy as code for teams and AI agents

action.yml's description is the summary the Marketplace shows. It now
leads with the line the project is putting at the front of its public
copy, as does the README's opening paragraph. The Marketplace reads
action.yml from a release, so the new summary reaches it with the next
release.

Author: shenxianpeng

README.md

@@ -21,10 +21,11 @@
 
 </div>
 
-The GitHub Action for [Commit Check](https://github.com/commit-check/commit-check).
-It checks every commit of a pull request — message, branch, author, and
-optionally the PR title — against your `cchk.toml`, and reports the result in
-the job summary, as annotations on the diff and, if you want, as a PR comment.
+The GitHub Action for [Commit Check](https://github.com/commit-check/commit-check),
+commit policy as code for teams and AI agents. It checks every commit of a pull
+request — message, branch, author, and optionally the PR title — against your
+`cchk.toml`, and reports the result in the job summary, as annotations on the
+diff and, if you want, as a PR comment.
 
 ## Usage
 

action.yml

@@ -1,5 +1,5 @@
 name: Commit Check Action
-description: Check commit message formatting, branch naming, committer name, email, and more
+description: "Commit policy as code for teams and AI agents: check every commit of a pull request against your cchk.toml"
 author: shenxianpeng
 branding:
   icon: "git-commit"