docs: add rules for agents working in this repo

AGENTS.md

@@ -0,0 +1,18 @@
+# Working in this repo
+
+Instructions for any coding agent.
+
+## This repository is public
+
+Anyone can read everything here: the pages, the OpenAPI file, commit messages, branch names, pull request titles and descriptions, review comments, and every earlier version of a pull request description.
+
+Write only what a customer needs to use Strettch Cloud. Never put any of these anywhere in this repo or its pull requests:
+
+- internal ticket numbers or titles, or links to private repositories, pull requests, documents or dashboards;
+- names of internal services, flags, fields, hosts, IP addresses or infrastructure;
+- how a feature is built, tested or rolled out, or what isn't finished yet;
+- anything that only makes sense to the Strettch Cloud team.
+
+Describe behaviour as a customer sees it. If a page can be published only once something ships, keep its pull request as a draft and leave the reason out of it. When unsure whether something is internal, leave it out and ask.
+
+Removing a mistake later doesn't make it private again. An edited pull request description keeps its earlier versions, and renaming the branch of an open pull request closes it. Get it right before you push.

CLAUDE.md

@@ -0,0 +1 @@
+@AGENTS.md