internal/gui: Wails app with Classic React variant + theme toggle

- app.go: App struct with stub bindings (RunCheck/StartEngine/
  StopEngine/GetStatus/Version) — emits check:result, check:done,
  engine:status, stats:update events. Real backend lands in Phase 1.
- run.go: wails.Run() with frameless 480x640 fixed window, Classic
  dark bg matching theme.
- embed.go: //go:embed all:frontend/dist for the Vite build output.
- frontend/: Vite + React project derived from `wails init -t react`.
  Removed default template assets and wired Classic variant from
  docs/design/v2/.
  - components/Classic.jsx: variant 1 with custom title bar
    (drag region, sun/moon theme toggle, min/close hooked to
    Wails WindowMinimise/Quit).
  - components/shared.jsx: useDrover hook adapted to call Wails
    bindings and listen on backend events instead of mock SCENARIOS.
    Added IconSun + IconMoon for the title-bar toggle.
  - App.jsx: owns mode state, wraps setMode in
    document.startViewTransition so the title-bar toggle gives a
    circle-reveal sweep from the cursor.
  - style.css: clean reset (overflow hidden, no scrollbars, brand
    background) — replaces the wails-react-template defaults.
  - wailsjs/go/gui/App.js: hand-written bindings since our App
    struct lives in package gui rather than the standard top-level
    main; `wails generate module` would have written package main
    bindings here.
- build/: standard wails artifacts (icon, manifest); will be
  consumed by `wails build` once we wire it through CI.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/gui/frontend/package.json

@@ -0,0 +1,21 @@
+{
+  "name": "frontend",
+  "private": true,
+  "version": "0.0.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "vite build",
+    "preview": "vite preview"
+  },
+  "dependencies": {
+    "react": "^18.2.0",
+    "react-dom": "^18.2.0"
+  },
+  "devDependencies": {
+    "@types/react": "^18.0.17",
+    "@types/react-dom": "^18.0.6",
+    "@vitejs/plugin-react": "^2.0.1",
+    "vite": "^3.0.7"
+  }
+}