Tune CI and dependabot config (#97)

* Group dependabot updates and add cooldown

Batch minor and patch GitHub Actions bumps into a single rolling PR and
keep coordinated major bumps together in their own group, so routine
updates land without waiting on major-bump review. Add a 7-day cooldown
so PRs wait for broken releases to be yanked or patched first.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* workflow: bump build/coverage to perldocker/perl-tester:5.42

* workflow: add concurrency block to cancel superseded runs

* workflow: install deps with setup-cpm + cpm install

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: oalders

.github/dependabot.yml

@@ -5,3 +5,17 @@ updates:
   schedule:
     # Check for updates to GitHub Actions every week
     interval: "weekly"
+  groups:
+    major-updates:
+      patterns:
+        - "*"
+      update-types:
+        - "major"
+    minor-and-patch:
+      patterns:
+        - "*"
+      update-types:
+        - "minor"
+        - "patch"
+  cooldown:
+    default-days: 7

.github/workflows/dzil-build-and-test.yml

@@ -10,12 +10,16 @@ on:
       - "*"
   workflow_dispatch:
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   build-job:
     name: Build distribution
     runs-on: ubuntu-latest
     container:
-      image: perldocker/perl-tester:5.38
+      image: perldocker/perl-tester:5.42
     steps:
       - uses: actions/checkout@v6
       - name: Run Tests
@@ -33,7 +37,7 @@ jobs:
     needs: build-job
     runs-on: ubuntu-latest
     container:
-      image: perldocker/perl-tester:5.38
+      image: perldocker/perl-tester:5.42
     steps:
       - uses: actions/checkout@v6 # codecov wants to be inside a Git repository
       - uses: actions/download-artifact@v7
@@ -105,9 +109,9 @@ jobs:
         with:
           name: build_dir
           path: .
-      - name: install deps using cpm
-        uses: perl-actions/install-with-cpm@v1
+      - uses: perl-actions/setup-cpm@v1
         with:
-          cpanfile: "cpanfile"
-          args: "--with-suggests --with-recommends --with-test"
+          version: compat
+      - name: install deps using cpm
+        run: cpm install -g --cpanfile cpanfile --with-suggests --with-recommends --with-test
       - run: prove -lr t