test(client): unit-test the pure-logic modules + wire coverage into CI/Sonar

Stand up a client test suite on Node's built-in runner (no vitest/jsdom — the
targeted modules are plain ESM with no browser/DOM deps) and cover the
meaningful client logic, not presentational components:

- api/client.js: the fetch wrapper — always sends the session cookie, maps a
  non-2xx response to a thrown ApiError (body.message → statusText fallback),
  resolves an empty body to null, sets Content-Type for JSON but NOT for raw
  FormData uploads, and builds/encodes query strings + path params.
- lib/shardEvents.js: describe() across event kinds (payload vs live frame,
  actor name→acct→"Someone" fallback, sale pluralization, champ.update
  branches) and the categoryOf table-consistency check.
- data/regionBuckets.js: the presence roll-up, incl. the first-match-wins
  ordering and the "buckets always reconcile to the total" invariant.
- lib/heroLayout.js: parseLayout's version/shape guard and heroBackground's
  default-vs-custom branch.
- lib/format.js: the date/label formatters + relative-time buckets.

Wiring so these actually count:
- client/package.json gains a `test` script (node --test);
- pr-checks.yml runs the client tests as a PR gate;
- sonarqube.yml generates a client LCOV report and sonar-project.properties
  feeds it alongside the server report (SF paths resolve to client/src/...).

43 client tests; coverage on the tested modules: format/regionBuckets/
heroLayout 100%, api client 86%, shardEvents 80%.

Co-Authored-By: Claude <noreply@anthropic.com>

.gitea/workflows/pr-checks.yml

@@ -52,6 +52,9 @@ jobs:
           cache-dependency-path: client/package-lock.json
       - name: Install client deps
         run: npm ci --prefix client
+      - name: Run client tests
+        # Pure-logic unit tests on Node's built-in runner (no browser/DOM).
+        run: npm test --prefix client
       - name: Build client
         run: npm run build --prefix client