ci: constrain vitest to a small fixed fork pool for the CI runner

'npm test' (default vitest thread pool) fails in ~1s on this Gitea Actions
runner for no reason reproducible locally (plain run, CI=true, and a fully
fresh rm -rf node_modules && npm ci all pass 215/215). Forcing the forks
pool with a small fixed worker count (min 1, max 2) is a standard fix for
this class of CI-only vitest worker-pool crash.

.github/workflows/build-verify.yml

@@ -79,4 +79,14 @@ jobs:
           exit $MISSING
 
       - name: vitest
-        run: npm test
+        run: npx vitest run --pool=forks --poolOptions.forks.minForks=1 --poolOptions.forks.maxForks=2 --reporter=verbose
+        # 2026-07-16: `npm test` (plain `vitest run`, default thread pool) fails in
+        # ~1s on this runner with no visible cause -- passes reliably every way
+        # tried locally (plain, CI=true, and a fully fresh `rm -rf node_modules &&
+        # npm ci`, all 215/215). A 1s failure with no per-test output strongly
+        # suggests a worker-pool crash specific to this runner's environment, not
+        # a real test regression. Forcing the forks pool with a small, fixed
+        # worker count is a common fix for that class of CI-only vitest failure.
+        # If this step is STILL red after this change, the failure is a runner
+        # environment issue outside what can be diagnosed from a local machine --
+        # needs someone with actual dashboard/log access to this Gitea instance.