[kube-prometheus-stack] Add agent skill for prometheus-operator bumps (#7013)

Signed-off-by: Ilia <ilia.lazebnik@gmail.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: DrFaust92

.agent/skills/bump-prometheus-operator/SKILL.md

@@ -0,0 +1,115 @@
+---
+name: bump-prometheus-operator
+description: >-
+  Bump the prometheus-operator version shipped by the kube-prometheus-stack
+  chart. Use when a new prometheus-operator/prometheus-operator release is out
+  and the chart's appVersion needs to follow it: syncs CRDs, checks for new CRD
+  kinds and RBAC changes, bumps the chart version, updates UPGRADE.md, and opens
+  a PR. Triggers on "bump prometheus-operator", "update kube-prometheus-stack to
+  the latest operator", "sync operator CRDs".
+---
+
+# Bump prometheus-operator in kube-prometheus-stack
+
+Promotes the `appVersion` of `charts/kube-prometheus-stack` to a new
+`prometheus-operator/prometheus-operator` release and brings everything that
+travels with the operator (CRDs, RBAC, upgrade notes) along with it.
+
+## Scope of an operator bump
+
+The operator version is the chart's `appVersion`. A bump touches a small,
+fixed set of files — mirror the most recent merged bump PR (search
+`git log --oneline -S "appVersion: v" -- charts/kube-prometheus-stack/Chart.yaml`)
+rather than improvising:
+
+- `charts/kube-prometheus-stack/Chart.yaml` — `appVersion` + chart `version`
+- `charts/kube-prometheus-stack/charts/crds/crds/crd-*.yaml` (10 CRDs) and
+  `charts/crds/files/crds.bz2` — regenerated, never hand-edited
+- `charts/kube-prometheus-stack/UPGRADE.md` — new section
+- `charts/kube-prometheus-stack/templates/prometheus-operator/clusterrole.yaml`
+  — only if the operator's RBAC actually changed (see step 4)
+
+## Procedure
+
+### 1. Find the target version & branch
+
+```bash
+# Latest non-prerelease operator tag
+curl -s https://api.github.com/repos/prometheus-operator/prometheus-operator/releases/latest | jq -r .tag_name
+git checkout -b kube-prometheus-stack-bump-operator-<vX.Y.Z> upstream/main
+```
+
+Always branch off a fresh `upstream/main` so the PR diff is just the bump.
+
+### 2. Bump Chart.yaml
+
+Set `appVersion` to the new `vX.Y.Z`. Bump the chart `version` following the
+precedent of the previous bump: historically a **minor** operator bump
+(e.g. `v0.91.0 → v0.92.0`) is released as a **major** chart bump
+(e.g. `86.x → 87.0.0`). Confirm the convention against the last bump PR.
+
+### 3. Regenerate CRDs
+
+`hack/update_crds.sh` reads `appVersion` from `Chart.yaml`, so bump Chart.yaml
+**first**, then:
+
+```bash
+bash charts/kube-prometheus-stack/hack/update_crds.sh
+```
+
+This downloads the 10 CRDs from
+`prometheus-operator/.../<appVersion>/example/prometheus-operator-crd/` and
+rebuilds `charts/crds/files/crds.bz2`.
+
+**Check for new CRD kinds** — if the operator added a CRD, the `FILES` array in
+`update_crds.sh` (and the `crds` subchart) must be extended:
+
+```bash
+diff \
+  <(curl -s "https://api.github.com/repos/prometheus-operator/prometheus-operator/contents/example/prometheus-operator-crd?ref=<OLD>" | jq -r '.[].name' | sort) \
+  <(curl -s "https://api.github.com/repos/prometheus-operator/prometheus-operator/contents/example/prometheus-operator-crd?ref=<NEW>" | jq -r '.[].name' | sort)
+```
+
+### 4. Check RBAC
+
+The chart's operator `ClusterRole` is maintained by hand, so confirm whether the
+operator's required RBAC changed between versions:
+
+```bash
+f=example/rbac/prometheus-operator/prometheus-operator-cluster-role.yaml
+diff \
+  <(curl -s "https://raw.githubusercontent.com/prometheus-operator/prometheus-operator/<OLD>/$f") \
+  <(curl -s "https://raw.githubusercontent.com/prometheus-operator/prometheus-operator/<NEW>/$f")
+```
+
+A diff in only the `app.kubernetes.io/version` label = **no change needed**.
+Any new/removed `rules` entry = update
+`templates/prometheus-operator/clusterrole.yaml` to match. Most patch/minor
+operator bumps need no RBAC change.
+
+### 5. Update UPGRADE.md
+
+Prepend a `## From <old-major>.x to <new-major>.x` section. Copy the previous
+section's wording and the 10 `kubectl apply --server-side -f .../<NEW>/...`
+CRD commands, swapping the version.
+
+### 6. Validate
+
+```bash
+cd charts/kube-prometheus-stack
+helm dependency build .        # required, or lint nil-pointers on subchart values
+helm lint .
+helm template t . | grep 'prometheus-operator:'   # must show the new vX.Y.Z
+```
+
+> CRDs live in the Helm-native `charts/crds/crds/` directory and are **not**
+> rendered by `helm template` — that is expected. The `crds.bz2` only feeds the
+> optional `crds.upgradeJob`.
+
+### 7. Commit & PR
+
+- Sign off (DCO) — see `CONTRIBUTING.md#sign-off-your-work`.
+- Title: `[kube-prometheus-stack] Bump prometheus-operator to vX.Y.Z`.
+- On review updates, add new commits — **do not squash** (the PR is squashed on
+  merge).
+- Fill the PR template; tick DCO + Chart Version bumped + title-starts-with-chart.