refactor: remove bundled Claude Code binary support

- Remove all bundled/sidecar binary functionality
- Delete build scripts for fetching and building Claude executables
- Simplify binary detection to only support system installations
- Update UI to remove bundled installation options
- Update build configuration and documentation

package.json

@@ -5,15 +5,8 @@
   "license": "AGPL-3.0",
   "type": "module",
   "scripts": {
-    "predev": "bun run build:executables:current",
     "dev": "vite",
     "build": "tsc && vite build",
-    "prebuild": "bun run build:executables:current",
-    "build:executables": "bun run scripts/fetch-and-build.js --version=1.0.41",
-    "build:executables:current": "bun run scripts/fetch-and-build.js current --version=1.0.41",
-    "build:executables:linux": "bun run scripts/fetch-and-build.js linux --version=1.0.41",
-    "build:executables:macos": "bun run scripts/fetch-and-build.js macos --version=1.0.41",
-    "build:executables:windows": "bun run scripts/fetch-and-build.js windows --version=1.0.41",
     "preview": "vite preview",
     "tauri": "tauri"
   },