Merge pull request #639 from IntersectMBO/f-f/update-contribution-policy

Update contribution policy to note how contributions should be vetted first

Author: lehins

CONTRIBUTING.md

@@ -1,6 +1,23 @@
-# Contributing to the Cardano BAse
+# Contributing to Cardano Base
 
-## Roles and responsibilities
+## Before You Contribute
+
+`cardano-base` is a foundational infrastructure library with downstream impact across the Cardano ecosystem.
+To protect the core team's review bandwidth and ensure all changes align with the project's direction,
+**we do not accept unsolicited contributions**.
+
+Comment on the issue you'd like to work on and wait for a maintainer to explicitly assign it to you.
+Pull requests for work that was not approved in advance will be closed without review.
+
+The reason for this process is that reviewing code in such a
+security-critical project is time-expensive, and we need to make sure both your time and the reviewers' time are well spent.
+
+Usage of AI tools for adding contributions to the repository is reserved for maintainers and core contributors only.
+Any pull request that was generated by AI or with use of AI will be immediately rejected.
+
+For security-related issues please consult the [disclosure policy for security vulnerabilities](./SECURITY.md).
+
+## Roles and Responsibilities
 
 Currently there are two core maintainers: