chore(ci): add Dependabot grouping, PR auto-labeler, and PR size warning

- Group Dependabot Go module updates: k8s.io/* together, remaining
  minor/patch together. Group all GitHub Actions updates into a single
  PR. Reduces weekly Dependabot PR noise from ~13 individual PRs to ~3.
- Add actions/labeler workflow to auto-label PRs by changed paths
  (area/api, area/controller, area/helm, area/ci, area/docs, area/e2e,
  area/cli).
- Add PR size labeler (xs/s/m/l/xl) with a warning comment on XL PRs
  (500+ lines) suggesting a split.

Closes #65
Closes #62
Closes #73

Signed-off-by: Sebastien Tardif <sebtardif@ncf.ca>

Author: SebTardif

.github/dependabot.yml

@@ -9,6 +9,18 @@ updates:
     open-pull-requests-limit: 5
     commit-message:
       prefix: "chore(deps)"
+    groups:
+      k8s:
+        patterns:
+          - "k8s.io/*"
+          - "sigs.k8s.io/*"
+      go-minor:
+        update-types:
+          - "minor"
+          - "patch"
+        exclude-patterns:
+          - "k8s.io/*"
+          - "sigs.k8s.io/*"
 
   - package-ecosystem: github-actions
     directory: /
@@ -19,6 +31,10 @@ updates:
     open-pull-requests-limit: 5
     commit-message:
       prefix: "chore(deps)"
+    groups:
+      actions:
+        patterns:
+          - "*"
 
   - package-ecosystem: docker
     directory: /

.github/labeler.yml

@@ -0,0 +1,33 @@
+area/api:
+  - changed-files:
+      - any-glob-to-any-file: "api/**"
+
+area/controller:
+  - changed-files:
+      - any-glob-to-any-file: "internal/**"
+
+area/helm:
+  - changed-files:
+      - any-glob-to-any-file: "charts/**"
+
+area/ci:
+  - changed-files:
+      - any-glob-to-any-file:
+          - ".github/**"
+          - "Makefile"
+
+area/docs:
+  - changed-files:
+      - any-glob-to-any-file:
+          - "docs/**"
+          - "*.md"
+
+area/e2e:
+  - changed-files:
+      - any-glob-to-any-file:
+          - "test/**"
+          - ".chainsaw.yaml"
+
+area/cli:
+  - changed-files:
+      - any-glob-to-any-file: "cmd/kubectl-attune/**"

.github/workflows/labeler.yaml

@@ -0,0 +1,22 @@
+name: PR Labeler
+on:
+  pull_request_target:
+    types: [opened, synchronize]
+
+permissions:
+  contents: read
+  pull-requests: write
+
+jobs:
+  label:
+    name: Auto-label PR
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - uses: step-security/harden-runner@9af89fc71515a100421586dfdb3dc9c984fbf411 # v2.19.4
+        with:
+          egress-policy: audit
+      - uses: actions/labeler@8558fd74291d67161a8a78ce36a881fa63b766a9 # v5.0.0
+        with:
+          configuration-path: .github/labeler.yml
+          sync-labels: true

.github/workflows/pr-size.yaml

@@ -0,0 +1,57 @@
+name: PR Size
+on:
+  pull_request_target:
+    types: [opened, synchronize]
+
+permissions:
+  contents: read
+  pull-requests: write
+
+jobs:
+  size-label:
+    name: Label PR size
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - uses: step-security/harden-runner@9af89fc71515a100421586dfdb3dc9c984fbf411 # v2.19.4
+        with:
+          egress-policy: audit
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+        with:
+          fetch-depth: 0
+          ref: ${{ github.event.pull_request.head.sha }}
+      - name: Calculate diff size and apply label
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+        run: |
+          ADDITIONS=${{ github.event.pull_request.additions }}
+          DELETIONS=${{ github.event.pull_request.deletions }}
+          TOTAL=$((ADDITIONS + DELETIONS))
+
+          if [ "$TOTAL" -lt 10 ]; then
+            SIZE="size/xs"
+          elif [ "$TOTAL" -lt 50 ]; then
+            SIZE="size/s"
+          elif [ "$TOTAL" -lt 250 ]; then
+            SIZE="size/m"
+          elif [ "$TOTAL" -lt 500 ]; then
+            SIZE="size/l"
+          else
+            SIZE="size/xl"
+          fi
+
+          echo "PR #${PR_NUMBER}: +${ADDITIONS} -${DELETIONS} = ${TOTAL} lines -> ${SIZE}"
+
+          # Remove any existing size labels, then add the correct one
+          for label in size/xs size/s size/m size/l size/xl; do
+            gh pr edit "$PR_NUMBER" --repo "${{ github.repository }}" --remove-label "$label" 2>/dev/null || true
+          done
+          gh pr edit "$PR_NUMBER" --repo "${{ github.repository }}" --add-label "$SIZE"
+
+          # Post a warning comment for XL PRs
+          if [ "$SIZE" = "size/xl" ]; then
+            gh pr comment "$PR_NUMBER" --repo "${{ github.repository }}" \
+              --body "> **Large PR** (+${ADDITIONS} -${DELETIONS} = ${TOTAL} lines). Consider splitting into smaller, focused PRs for easier review." \
+              2>/dev/null || true
+          fi