Add Playwright E2E testing infrastructure

- Add playwright-web-flake to flake.nix for NixOS browser support
- Pin @playwright/test@1.56.1 to match nixpkgs version
- Create playwright.config.ts with Chromium-only, auto-start dev server
- Add e2e/smoke.spec.ts with initial smoke tests
- Add .mcp.json for Claude browser control via MCP
- Update .gitignore for playwright artifacts
- Remove E2E test skip from spec.md Known Limitations
- Update specs/testing.md to require three-tier testing approach

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

pnpm-lock.yaml

@@ -25,7 +25,7 @@ importers:
         version: 0.562.0(react@19.2.3)
       next:
         specifier: 16.1.1
-        version: 16.1.1(@babel/core@7.28.5)(@opentelemetry/api@1.9.0)(react-dom@19.2.3(react@19.2.3))(react@19.2.3)
+        version: 16.1.1(@babel/core@7.28.5)(@opentelemetry/api@1.9.0)(@playwright/test@1.56.1)(react-dom@19.2.3(react@19.2.3))(react@19.2.3)
       node-cron:
         specifier: ^4.2.1
         version: 4.2.1
@@ -57,6 +57,9 @@ importers:
       '@biomejs/biome':
         specifier: 2.3.11
         version: 2.3.11
+      '@playwright/test':
+        specifier: 1.56.1
+        version: 1.56.1
       '@tailwindcss/postcss':
         specifier: ^4
         version: 4.1.18
@@ -974,6 +977,11 @@ packages:
   '@pinojs/redact@0.4.0':
     resolution: {integrity: sha512-k2ENnmBugE/rzQfEcdWHcCY+/FM3VLzH9cYEsbdsoqrvzAKRhUZeRNhAZvB8OitQJ1TBed3yqWtdjzS6wJKBwg==}
 
+  '@playwright/test@1.56.1':
+    resolution: {integrity: sha512-vSMYtL/zOcFpvJCW71Q/OEGQb7KYBPAdKh35WNSkaZA75JlAO8ED8UN6GUNTm3drWomcbcqRPFqQbLae8yBTdg==}
+    engines: {node: '>=18'}
+    hasBin: true
+
   '@rolldown/pluginutils@1.0.0-beta.53':
     resolution: {integrity: sha512-vENRlFU4YbrwVqNDZ7fLvy+JR1CRkyr01jhSiDpE1u6py3OMzQfztQU2jxykW3ALNxO4kSlqIDeYyD0Y9RcQeQ==}
 
@@ -1553,6 +1561,11 @@ packages:
       picomatch:
         optional: true
 
+  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}
@@ -1778,6 +1791,16 @@ packages:
     resolution: {integrity: sha512-3qqVfpJtRQUCAOs4rTOEwLH6mwJJ/CSAlbis8fKOiMzTtXh0HN/VLsn3UWVTJ7U8DsWmxeNon2IpGb+wORXH4g==}
     hasBin: true
 
+  playwright-core@1.56.1:
+    resolution: {integrity: sha512-hutraynyn31F+Bifme+Ps9Vq59hKuUCz7H1kDOcBs+2oGguKkWTU50bBWrtz34OUWmIwpBTWDxaRPXrIXkgvmQ==}
+    engines: {node: '>=18'}
+    hasBin: true
+
+  playwright@1.56.1:
+    resolution: {integrity: sha512-aFi5B0WovBHTEvpM3DzXTUaeN6eN0qWnTkKx4NQaH4Wvcmc153PdaY2UBdSYKaGYw+UyWXSVyxDUg5DoPEttjw==}
+    engines: {node: '>=18'}
+    hasBin: true
+
   pocketbase@0.26.5:
     resolution: {integrity: sha512-SXcq+sRvVpNxfLxPB1C+8eRatL7ZY4o3EVl/0OdE3MeR9fhPyZt0nmmxLqYmkLvXCN9qp3lXWV/0EUYb3MmMXQ==}
 
@@ -2723,6 +2746,10 @@ snapshots:
 
   '@pinojs/redact@0.4.0': {}
 
+  '@playwright/test@1.56.1':
+    dependencies:
+      playwright: 1.56.1
+
   '@rolldown/pluginutils@1.0.0-beta.53': {}
 
   '@rollup/rollup-android-arm-eabi@4.55.1':
@@ -3213,6 +3240,9 @@ snapshots:
     optionalDependencies:
       picomatch: 4.0.3
 
+  fsevents@2.3.2:
+    optional: true
+
   fsevents@2.3.3:
     optional: true
 
@@ -3363,7 +3393,7 @@ snapshots:
 
   nanoid@3.3.11: {}
 
-  next@16.1.1(@babel/core@7.28.5)(@opentelemetry/api@1.9.0)(react-dom@19.2.3(react@19.2.3))(react@19.2.3):
+  next@16.1.1(@babel/core@7.28.5)(@opentelemetry/api@1.9.0)(@playwright/test@1.56.1)(react-dom@19.2.3(react@19.2.3))(react@19.2.3):
     dependencies:
       '@next/env': 16.1.1
       '@swc/helpers': 0.5.15
@@ -3383,6 +3413,7 @@ snapshots:
       '@next/swc-win32-arm64-msvc': 16.1.1
       '@next/swc-win32-x64-msvc': 16.1.1
       '@opentelemetry/api': 1.9.0
+      '@playwright/test': 1.56.1
       sharp: 0.34.5
     transitivePeerDependencies:
       - '@babel/core'
@@ -3426,6 +3457,14 @@ snapshots:
       sonic-boom: 4.2.0
       thread-stream: 4.0.0
 
+  playwright-core@1.56.1: {}
+
+  playwright@1.56.1:
+    dependencies:
+      playwright-core: 1.56.1
+    optionalDependencies:
+      fsevents: 2.3.2
+
   pocketbase@0.26.5: {}
 
   postcss@8.4.31: