feat: enable Computer Use on Windows and Linux (#145)

Remove macOS-only guards so Computer Use works cross-platform:
- main.tsx: allow CHICAGO_MCP on any known platform (not just macos)
- swiftLoader.ts: remove darwin-only throw, let the backend handle it
- computer-use-input: dispatch to darwin/win32/linux backends
- computer-use-swift: rename loadDarwin→loadBackend, dispatch all platforms

Co-authored-by: yi7503 <yi7503@gmail.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/@ant/computer-use-input/src/index.ts

@@ -22,12 +22,18 @@ export interface InputBackend {
 }
 
 function loadBackend(): InputBackend | null {
-  if (process.platform !== 'darwin') return null
   try {
-    return require('./backends/darwin.js') as InputBackend
+    if (process.platform === 'darwin') {
+      return require('./backends/darwin.js') as InputBackend
+    } else if (process.platform === 'win32') {
+      return require('./backends/win32.js') as InputBackend
+    } else if (process.platform === 'linux') {
+      return require('./backends/linux.js') as InputBackend
+    }
   } catch {
     return null
   }
+  return null
 }
 
 const backend = loadBackend()