feat: initial Playwright smoke suite

20 tests across 5 files covering all plugin surfaces on staging:
- Homepage load and PHP fatal detection
- Reconstitution Calculator shortcode + math
- Peptide Search AI widget + AJAX response
- Admin: all plugins active, PSA + PRAutoBlogger settings pages
- REST API: prc/v1/presets, peptides/v1/search, compounds, CPT types

Staging shortcode pages:
  /reconstitution-calculator/ - [prc_calculator]
  /search-peptides/           - [peptide_search]
  /peptide-directory/         - [peptide_directory]

GHA workflow: smoke.yml supports manual dispatch + workflow_call
for use as a deploy gate from plugin repos.

playwright.config.ts

@@ -0,0 +1,61 @@
+/**
+ * Playwright configuration for peptiderepo.com smoke tests.
+ *
+ * Usage:
+ *   npm test                          — run against BASE_URL (defaults to staging)
+ *   npm run test:staging              — explicit staging run
+ *   npm run test:prod                 — production smoke run
+ *
+ * Environment variables (set in .env or CI secrets):
+ *   BASE_URL                 — target site root (default: https://staging.peptiderepo.com)
+ *   WP_ADMIN_USER            — WordPress admin username
+ *   WP_ADMIN_PASSWORD        — WordPress admin password
+ *   CALC_PAGE_PATH           — URL path to the reconstitution calculator page (default: /reconstitution-calculator/)
+ *   SEARCH_PAGE_PATH         — URL path to the peptide search page (default: /)
+ *   DIRECTORY_PAGE_PATH      — URL path to the peptide directory page (default: /peptides/)
+ */
+
+import { defineConfig, devices } from '@playwright/test';
+import * as dotenv from 'dotenv';
+import * as path from 'path';
+
+dotenv.config({ path: path.resolve(__dirname, '.env') });
+
+const BASE_URL = process.env.BASE_URL ?? 'https://staging.peptiderepo.com';
+
+export default defineConfig({
+  testDir: './tests',
+  fullyParallel: false,          // WP staging is single-server; parallel can cause rate-limit hits
+  forbidOnly: !!process.env.CI,  // Prevent .only from landing in CI
+  retries: process.env.CI ? 1 : 0,
+  workers: 1,                    // Sequential against staging to be polite
+  reporter: process.env.CI
+    ? [['github'], ['html', { open: 'never' }]]
+    : [['list'], ['html', { open: 'on-failure' }]],
+
+  use: {
+    baseURL: BASE_URL,
+    trace: 'on-first-retry',
+    screenshot: 'only-on-failure',
+    video: 'retain-on-failure',
+    actionTimeout: 15_000,
+    navigationTimeout: 30_000,
+  },
+
+  projects: [
+    // Auth setup — runs first, saves session to disk
+    {
+      name: 'setup',
+      testMatch: /global\.setup\.ts/,
+    },
+    // All smoke tests — depend on auth setup
+    {
+      name: 'chromium',
+      use: {
+        ...devices['Desktop Chrome'],
+        storageState: 'playwright/.auth/admin.json',
+      },
+      dependencies: ['setup'],
+    },
+  ],
+});