Run the engine specs before mirroring and publishing

The engine's 180 specs were never run by CI: the mirror repo is
generated by a subtree split, so a pipeline committed there would be
overwritten on the next sync, and the monorepo's own pipeline only
mirrored and published. A broken engine could reach the gem registry.

The test now gates both — it runs on the same trigger the mirror does
(a change under libs/ruby/warp_engine), and the steps after it only run
if it passes. The specs need MySQL, hence the service, and a prepared
test database: on a fresh database maintain_test_schema! reports the
engine's own migrations as pending instead of loading the schema.

Verified by running the step as written in a clean ruby:3.2 container
against a fresh mysql:8 — 180 examples, 0 failures.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.woodpecker.yaml

@@ -21,7 +21,37 @@ clone:
       partial: false
       depth: 0 # a subtree splithez teljes history kell
 
+services:
+  - name: mysql
+    image: mysql:8
+    environment:
+      MYSQL_ALLOW_EMPTY_PASSWORD: "yes"
+      MYSQL_DATABASE: warp_engine_test
+
 steps:
+  # A motor tesztje kapuzza a tobbit: ha bukik, se a tukrozes, se a gem
+  # kiadasa nem fut le. A mirror repoba nincs ertelme CI-t tenni, mert azt a
+  # subtree split minden alkalommal feluliria.
+  test-engine:
+    image: ruby:3.2
+    environment:
+      RAILS_ENV: test
+      DB_HOST: mysql
+    commands:
+      - apt-get update && apt-get install -y --no-install-recommends default-libmysqlclient-dev
+      - cd libs/ruby/warp_engine
+      - bundle install --jobs 4
+      - |
+        echo "==> Varakozas a mysql-re"
+        for i in $(seq 1 60); do
+          if mysqladmin ping -h mysql --silent 2>/dev/null; then break; fi
+          sleep 2
+        done
+      - |
+        echo "==> Teszt adatbazis elokeszitese"
+        bundle exec rake app:db:test:prepare
+      - bundle exec rspec
+
   split-mirror:
     image: alpine/git
     environment: