Scope CI-integ-test concurrency groups per-branch

The concurrency groups used fixed names spanning all branches, so a push
to main could cancel a pending PR run (and vice versa), leaving PRs not
fully tested.

Append ${{ github.ref }} to each group so runs only supersede pending
runs on the same branch, while different branches run in parallel. Also
drop the `queue: max` key, which is not a valid GitHub Actions
concurrency option and was ignored.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.github/workflows/ci-integ-test.yml

@@ -28,9 +28,8 @@ jobs:
     needs: build-distribution
     uses: ./.github/workflows/suite-integ-test-caching.yml
     concurrency:
-      group: CI-integ-test-caching
+      group: CI-integ-test-caching-${{ github.ref }}
       cancel-in-progress: false
-      queue: max
     with:
       skip-dist: false
     secrets: inherit
@@ -41,9 +40,8 @@ jobs:
     needs: caching-integ-tests
     uses: ./.github/workflows/suite-integ-test-other.yml
     concurrency:
-      group: CI-integ-test-other
+      group: CI-integ-test-other-${{ github.ref }}
       cancel-in-progress: false
-      queue: max
     with:
       skip-dist: false
     secrets: inherit
@@ -54,9 +52,8 @@ jobs:
     needs: other-integ-tests
     uses: ./.github/workflows/suite-integ-test-dependency-submission.yml
     concurrency:
-      group: CI-integ-test-dependency-submission
+      group: CI-integ-test-dependency-submission-${{ github.ref }}
       cancel-in-progress: false
-      queue: max
     with:
       skip-dist: false
     secrets: inherit