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

.gitea/workflows/check.yml

@@ -7,8 +7,6 @@ concurrency:
 jobs:
     check:
         runs-on: ubuntu-latest
-        # Free the shared runner from a hung build.
-        timeout-minutes: 20
         steps:
             # actions/checkout v4.2.2, 2026-02-22
             - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
@@ -17,4 +15,7 @@ jobs:
                   persist-credentials: false
                   # All history and tags, so git describe finds the version tag.
                   fetch-depth: 0
+            # Free the shared runner from a hung build. The limit is on the
+            # step because the runner ignores a job's timeout-minutes.
             - run: script/cibuild
+              timeout-minutes: 20