docs: prohibit committing autogenerated code

AGENTS.md

@@ -8,6 +8,20 @@
 - For cross-module work, apply every relevant scoped instruction file and
   completion workflow.
 
+## Autogenerated code
+
+- Never commit autogenerated code to the repository. This applies to backend,
+  frontend, shared packages, and every other module, including generated
+  protobuf bindings, API clients, serializers, and framework-generated code.
+- Commit the source definitions, generator configuration, and reproducible
+  generation commands instead. Generate code locally or during build and CI
+  workflows before any dependent validation or compilation steps.
+- Keep generated outputs ignored by Git. Do not force-add ignored generated
+  files or copy generated code into tracked source files.
+- Change the source definitions or generator inputs rather than editing
+  generated outputs. Document the generation workflow so a clean checkout can
+  build without committed generated code.
+
 ## Data and state architecture
 
 Preserve explicit **DTO → mapper → service → data model → provider → UI**