docs: add AGENTS instructions

Author: povilasv

AGENTS.md

@@ -0,0 +1,11 @@
+# AGENTS Instructions for Codex
+
+These instructions apply to all development via the Codex web UI.
+
+- Limit modifications to the `charts/opentelemetry-collector` folder when updating the chart.
+- After changing files in that folder:
+  1. Bump the chart version in `Chart.yaml`.
+  2. Update the `CHANGELOG` accordingly.
+  3. Run `make generate-examples CHARTS=opentelemetry-collector` to regenerate example manifests.
+  4. Commit the regenerated examples along with your other changes.
+