feat: 实现 4 个 NAPI 包 — modifiers/image-processor/audio-capture/url-handler

- modifiers-napi: 使用 Bun FFI 调用 macOS CGEventSourceFlagsState 检测修饰键
- image-processor-napi: 集成 sharp 库，macOS 剪贴板图像读取 (osascript)
- audio-capture-napi: 基于 SoX/arecord 的跨平台音频录制
- url-handler-napi: 完善函数签名（保持 null fallback）
- 修复 image-processor 类型兼容性问题

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

src/tools/FileReadTool/imageProcessor.ts

@@ -44,9 +44,9 @@ export async function getImageProcessor(): Promise<SharpFunction> {
     try {
       // Use the native image processor module
       const imageProcessor = await import('image-processor-napi')
-      const sharp = (imageProcessor as Record<string, SharpFunction>).sharp || imageProcessor.default
-      imageProcessorModule = { default: sharp }
-      return sharp
+      const sharpFn = (imageProcessor.sharp ?? imageProcessor.default) as SharpFunction
+      imageProcessorModule = { default: sharpFn }
+      return sharpFn
     } catch {
       // Fall back to sharp if native module is not available
       // biome-ignore lint/suspicious/noConsole: intentional warning