Fix setup project: override testDir to repo root so global.setup.ts is found

The top-level testDir is './tests', which scopes Playwright's file discovery.
global.setup.ts lives at repo root, so the setup project's testMatch regex
never got a chance to match — Playwright silently ran 0 setup tests, the
storage-state file at playwright/.auth/admin.json was never written, and
every dependent test failed on storageState load with ENOENT.

Adding 'testDir: \".\"' on the setup project lets Playwright scan repo root
for files matching the testMatch regex without affecting the chromium
project, which still uses the top-level './tests' testDir.

Bug present since the initial smoke suite (d46a1e4). Has been blocking
PRAutoBlogger workflow-driven prod deploys since the smoke gate was added
on 2026-04-26 (prautoblogger 96f0248d). v0.14.0 and v0.15.0 reached prod
via manual SSH rsync outside the workflow.

Agent-Session: cto peptide-e2e-setup-project-fix

playwright.config.ts

@@ -43,9 +43,14 @@ export default defineConfig({
   },
 
   projects: [
-    // Auth setup — runs first, saves session to disk
+    // Auth setup — runs first, saves session to disk.
+    // testDir override: global.setup.ts lives at repo root, not under ./tests.
+    // Without this, the top-level testDir './tests' filters it out and the
+    // setup project silently runs 0 tests, leaving the storage-state file
+    // unwritten and every chromium-project test failing on storageState load.
     {
       name: 'setup',
+      testDir: '.',
       testMatch: /global\.setup\.ts/,
     },
     // All smoke tests — depend on auth setup