Pin playwright@1.52.0 to match Docker image + add pre-stage Dockerfile

npm install playwright pulled v1.59.1 but the Docker image ships
v1.52.0 browsers, causing a version mismatch crash. Pin to 1.52.0.

Also add ci/Dockerfile.test-runner for pre-building the image into
registry.gobha.me:5000/ci-test-runner:latest — eliminates npm install
from every CI run.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ci/Dockerfile.test-runner

@@ -0,0 +1,11 @@
+# ci/Dockerfile.test-runner — Pre-built Playwright test runner
+#
+# Build & push (one-time, repeat when Playwright version bumps):
+#   docker build -t registry.gobha.me:5000/ci-test-runner:latest -f ci/Dockerfile.test-runner .
+#   docker push registry.gobha.me:5000/ci-test-runner:latest
+#
+# The CI compose override uses this image directly, avoiding npm install
+# on every run. Only the ci/ scripts are COPY'd at compose build time.
+FROM mcr.microsoft.com/playwright:v1.52.0-noble
+WORKDIR /work
+RUN npm init -y && npm install playwright@1.52.0

docker-compose.ci.yml

@@ -30,7 +30,7 @@ services:
       dockerfile_inline: |
         FROM mcr.microsoft.com/playwright:v1.52.0-noble
         WORKDIR /work
-        RUN npm init -y && npm install playwright
+        RUN npm init -y && npm install playwright@1.52.0
         COPY ci/ /work/ci/
         RUN chmod +x /work/ci/*.sh
     depends_on: