CI time limit on the step; no timeout in Dockerfile or scripts (closes #199)

The runner ignores a job's timeout-minutes, so the 20-minute limit moves
to the step that runs script/cibuild. The Dockerfile frontend-test stage,
script/frontend-test and script/frontend-viewport-test drop their timeout
wrappers, which failed make check on a busy host. go test's -timeout 90s
stays, as REPO_POLICIES.md requires it.

Model: opus-5-5

Dockerfile

@@ -62,9 +62,9 @@ WORKDIR /app
 COPY package.json yarn.lock ./
 RUN yarn install --frozen-lockfile
 COPY . .
-RUN NODE_OPTIONS=--test-reporter=dot timeout 90 yarn --silent run test || \
+RUN NODE_OPTIONS=--test-reporter=dot yarn --silent run test || \
     { echo "--- Rerunning with every test listed for details ---"; \
-      NODE_OPTIONS=--test-reporter=spec timeout 90 yarn --silent run test; \
+      NODE_OPTIONS=--test-reporter=spec yarn --silent run test; \
       exit 1; }
 
 # Test phase: the backend's tests with the race detector and coverage,