docs: add AGENTS.md with dev workflow conventions

AGENTS.md

@@ -0,0 +1,12 @@
+# AGENTS.md
+
+Personal development conventions — applies to all projects unless overridden by a project-level AGENTS.md.
+
+## Workflow
+
+- New feature → clean branch from `origin/master` → push → PR on Gitea
+- Branch naming: `feat/description` (features), `fix/description` (bugs/docs/docs/chores)
+- Always branch from `origin/master`, never from another feature branch
+- PR title describes the change; body explains motivation + summary
+- After PR merge, delete the feature branch
+- Always validate before push (build, lint, test)