test: add Playwright E2E infrastructure with smoke test

Set up Playwright with Chromium, dev server auto-start, test helpers
for seeding bots and programmatic auth. Added smoke spec that verifies
homepage and leaderboard load without crashes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pnpm-lock.yaml

@@ -12,6 +12,9 @@ importers:
 
   .:
     devDependencies:
+      '@playwright/test':
+        specifier: ^1.58.2
+        version: 1.58.2
       '@typescript-eslint/eslint-plugin':
         specifier: ^8.56.1
         version: 8.56.1(@typescript-eslint/parser@8.56.1(eslint@10.0.3(jiti@2.6.1))(typescript@5.9.3))(eslint@10.0.3(jiti@2.6.1))(typescript@5.9.3)
@@ -1131,6 +1134,11 @@ packages:
     resolution: {integrity: sha512-+1VkjdD0QBLPodGrJUeqarH8VAIvQODIbwh9XpP5Syisf7YoQgsJKPNFoqqLQlu+VQ/tVSshMR6loPMn8U+dPg==}
     engines: {node: '>=14'}
 
+  '@playwright/test@1.58.2':
+    resolution: {integrity: sha512-akea+6bHYBBfA9uQqSYmlJXn61cTa+jbO87xVLCWbTqbWadRVmhxlXATaOjOgcBaWU4ePo0wB41KMFv3o35IXA==}
+    engines: {node: '>=18'}
+    hasBin: true
+
   '@protobufjs/aspromise@1.1.2':
     resolution: {integrity: sha512-j+gKExEuLmKwvz3OgROXtrJ2UG2x8Ch2YZUxahh+s1F2HZ+wAceUNLkvy6zKCPVRkU++ZWQrdxsUeQXmcg4uoQ==}
 
@@ -2277,6 +2285,11 @@ packages:
     resolution: {integrity: sha512-hcg3ZmepS30/7BSFqRvoo3DOMQu7IjqxO5nCDt+zM9XWjb33Wg7ziNT+Qvqbuc3+gWpzO02JubVyk2G4Zvo1OQ==}
     engines: {node: '>=10'}
 
+  fsevents@2.3.2:
+    resolution: {integrity: sha512-xiqMQR4xAeHTuB9uWm+fFRcIOgKBMiOBP+eXiyT7jsgVCq1bkVygt00oASowB7EdtpOHaaPgKt812P9ab+DDKA==}
+    engines: {node: ^8.16.0 || ^10.6.0 || >=11.0.0}
+    os: [darwin]
+
   fsevents@2.3.3:
     resolution: {integrity: sha512-5xoDfX+fL7faATnagmWPpbFtwh/R77WmMMqqHGS65C3vvB0YHrgF+B1YmZ3441tMj5n63k0212XNoJwzlhffQw==}
     engines: {node: ^8.16.0 || ^10.6.0 || >=11.0.0}
@@ -2962,6 +2975,16 @@ packages:
   platform@1.3.6:
     resolution: {integrity: sha512-fnWVljUchTro6RiCFvCXBbNhJc2NijN7oIQxbwsyL0buWJPG85v81ehlHI9fXrJsMNgTofEoWIQeClKpgxFLrg==}
 
+  playwright-core@1.58.2:
+    resolution: {integrity: sha512-yZkEtftgwS8CsfYo7nm0KE8jsvm6i/PTgVtB8DL726wNf6H2IMsDuxCpJj59KDaxCtSnrWan2AeDqM7JBaultg==}
+    engines: {node: '>=18'}
+    hasBin: true
+
+  playwright@1.58.2:
+    resolution: {integrity: sha512-vA30H8Nvkq/cPBnNw4Q8TWz1EJyqgpuinBcHET0YVJVFldr8JDNiU9LaWAE1KqSkRYazuaBhTpB5ZzShOezQ6A==}
+    engines: {node: '>=18'}
+    hasBin: true
+
   possible-typed-array-names@1.1.0:
     resolution: {integrity: sha512-/+5VFTchJDoVj3bhoqi6UeymcD00DAwb1nJwamzPvHEszJ4FpF6SNNbUbOS8yI56qHzdV8eK0qEfOSiodkTdxg==}
     engines: {node: '>= 0.4'}
@@ -4729,6 +4752,10 @@ snapshots:
   '@pkgjs/parseargs@0.11.0':
     optional: true
 
+  '@playwright/test@1.58.2':
+    dependencies:
+      playwright: 1.58.2
+
   '@protobufjs/aspromise@1.1.2': {}
 
   '@protobufjs/base64@1.1.2': {}
@@ -5898,6 +5925,9 @@ snapshots:
       jsonfile: 6.2.0
       universalify: 2.0.1
 
+  fsevents@2.3.2:
+    optional: true
+
   fsevents@2.3.3:
     optional: true
 
@@ -6552,6 +6582,14 @@ snapshots:
 
   platform@1.3.6: {}
 
+  playwright-core@1.58.2: {}
+
+  playwright@1.58.2:
+    dependencies:
+      playwright-core: 1.58.2
+    optionalDependencies:
+      fsevents: 2.3.2
+
   possible-typed-array-names@1.1.0: {}
 
   postcss@8.5.8: