ci(tests): run the gated real-Postgres .picpeak cases in the backend job (#1058)

Stable backport of #1056 (main: 18b1e0f6). Change content is byte-identical
to the main twin.

The .picpeak restore suites gate their Postgres cases behind
PICPEAK_PG_TEST_URL and describe.skip themselves out when it is unset. The
variable is set in no workflow, so those cases have never run in CI.

On this branch the effect lands together with the #1041 backport, which brings
picpeakCrossEngine.test.js and its three real-Postgres stored-value cases —
stable has no picpeakRestorePg.test.js, so before that PR this wires up a
service nothing reads yet. Merging it first keeps the two twins mirroring
their main counterparts one-for-one instead of folding both into one PR.

Co-authored-by: Paul Nothaft <paul@MacStudio-von-Paul.local>

.github/workflows/tests.yml

@@ -30,6 +30,29 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 10
 
+    # The .picpeak restore suites gate their real-Postgres cases behind
+    # PICPEAK_PG_TEST_URL and `describe.skip` themselves out when it is
+    # unset — so until now they never ran here. That hid the half that
+    # matters: sequence resync, operator/role preservation across a
+    # cross-instance restore, and (with #1041) whether a SQLite-shaped
+    # row actually lands in Postgres with the right STORED VALUES rather
+    # than merely not throwing. Everything else in the suite still runs
+    # on SQLite; this service only un-gates those cases.
+    services:
+      postgres:
+        image: postgres:15-alpine
+        env:
+          POSTGRES_USER: picpeak
+          POSTGRES_PASSWORD: testpass
+          POSTGRES_DB: picpeak_test
+        options: >-
+          --health-cmd "pg_isready -U picpeak -d picpeak_test"
+          --health-interval 2s
+          --health-timeout 2s
+          --health-retries 30
+        ports:
+          - 5432:5432
+
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
@@ -52,6 +75,9 @@ jobs:
           # The S3 path itself is covered separately by the integration
           # suite when MinIO is provisioned.
           SKIP_S3_TESTS: 'true'
+          # Un-gates the real-Postgres cases in the .picpeak restore suites
+          # (see the `services:` note above). Absent it they silently skip.
+          PICPEAK_PG_TEST_URL: 'postgres://picpeak:testpass@127.0.0.1:5432/picpeak_test'
         run: |
           # Excluded suites — fail on upstream/beta too, tracked
           # separately as test-infra debt: