chore: add section on helm versioning

Author: lhoupert

RELEASING.md

@@ -15,6 +15,21 @@ Releases are automated via [release-please](https://github.com/googleapis/releas
 
 The Helm chart (`deployment/k8s/charts/`) is versioned independently from the Python package. release-please opens a separate helm release PR when commits touch files under `deployment/k8s/charts/`. That PR bumps `version:` in `Chart.yaml` and updates `deployment/k8s/charts/CHANGELOG.md`. The resulting GitHub release is tagged `helm-vX.Y.Z`.
 
+**Commit messages matter for chart releases.** A chart version bump only happens when a commit both:
+- touches at least one file under `deployment/k8s/charts/`, **and**
+- uses a bump-triggering type (`fix:`, `feat:`, or a breaking change)
+
+`chore:`, `ci:`, `docs:`, and other non-bumping types that touch chart files are valid conventional commits but will **not** produce a chart release. Use them for housekeeping that doesn't warrant a version bump (e.g. updating CI config, fixing a comment).
+
+Examples:
+
+```
+fix(helm): correct resource limit defaults         → patch bump
+feat(helm): add support for extra environment vars → minor bump
+feat(helm)!: rename required value X to Y         → major bump
+chore(helm): update maintainer list               → no bump
+```
+
 ## Commit message convention
 
 Version bumps follow [semantic versioning](https://semver.org/) based on commit type: