chore(ai): add AGENTS.md to improve assisted contributions

.github/copilot-instructions.md

@@ -1,9 +1,3 @@
 ## Copilot Instructions for ScyllaDB Operator
 
-Follow the project's [CONTRIBUTING.md](../CONTRIBUTING.md) and [API_CONVENTIONS.md](../API_CONVENTIONS.md).
-
-### Commits and PRs
-
-- Format commit messages and PR titles as [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0/): `<type>(<scope>): <subject>` or `<type>: <scopeless subject>`, where subject is imperative, lowercase, ≤72 chars, and has no trailing period. 
-- Never include `@mentions`, [keywords that close issues](https://docs.github.com/en/issues/tracking-your-work-with-issues/using-issues/linking-a-pull-request-to-an-issue) or hashtag ("#") references in the commit messages. 
-- If the PR fixes an issue, reference it with `Resolves #<number>` only in the PR description.
+Read and follow the instructions in [AGENTS.md](AGENTS.md) and all referred files in it for the project conventions and guidelines.

AGENTS.md

@@ -0,0 +1,11 @@
+# AGENTS.md
+
+This file provides instructions for AI coding agents contributing to this repository.
+
+## Guidelines
+
+Read and follow these documents before making changes:
+
+- [CONTRIBUTING.md](CONTRIBUTING.md) — development setup, build and test commands, coding conventions, commit and PR requirements.
+- [API_CONVENTIONS.md](API_CONVENTIONS.md) — API design patterns for CRD types.
+

CLAUDE.md

@@ -0,0 +1,3 @@
+# Claude Code Instructions
+
+Read and follow the instructions in [AGENTS.md](AGENTS.md) and all referred files in it for the project conventions and guidelines.

CONTRIBUTING.md

@@ -103,10 +103,12 @@ Once you have implemented the feature or bug fix in your branch, open a PR to th
 - Your commit history is clean.
 - Your commit message and PR title follow the guidelines outlined in this section.
 - If your changes are user-facing, you have added an appropriate entry to the changelog.
+- If the PR fixes an issue, reference it with `Resolves #<number>` only in the PR description.
 
 ### Commit History
 
 To maintain a clean commit history, aim for a minimal number of logical commits. Typically, this means a single commit that contains all the changes, with a separate commit for autogenerated parts.
+Never include `@mentions`, [keywords that close issues](https://docs.github.com/en/issues/tracking-your-work-with-issues/using-issues/linking-a-pull-request-to-an-issue) or hashtag ("#") references in the commit messages.
 
 ### Commits and PRs