ci(portal-self-service): run Vitest ahead of the production build to stop worker-start timeout (refs #68)

The frontend lane ran `nx run-many -t lint test build`, so the ~5min
self-service production build shared nx's task pool with the Vitest test
worker. @angular/build:unit-test's Vitest worker has hard-coded 60s/90s
startup timeouts (not configurable); on a CPU-constrained CI runner the
concurrent build starved the worker and it failed with "Timeout waiting
for worker to respond" — flaky, since it passed on the prior commit.

Split the target into a light lint+test phase and a separate build phase
so tests get CPU and the worker starts well inside its window.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Makefile

@@ -50,9 +50,16 @@ endif
 ci: lint build unit mutation frontend verify
 
 ## frontend: install deps and run the Nx lint/test/build for the portals (pnpm + Node required)
+# Tests run in their own phase, ahead of the build. The @angular/build:unit-test
+# (Vitest) runner spawns a worker with a hard-coded 60s/90s startup timeout that is
+# not configurable. When the ~5min production build shares the run-many pool, it
+# starves that worker of CPU on constrained CI runners and Vitest fails with
+# "Timeout waiting for worker to respond". Splitting the phases keeps tests off the
+# heavy build's back so the worker starts well inside its window.
 frontend:
 	pnpm install --frozen-lockfile
-	pnpm nx run-many -t lint test build
+	pnpm nx run-many -t lint test
+	pnpm nx run-many -t build
 
 ## lint: verify formatting (no changes)
 lint: