build: Vite 单文件构建 + 修复 doubaoime-asr 打包后 WASM 加载失败

- vite.config.ts: codeSplitting: false 替代多 chunk 输出，产出单文件 dist/cli.js
- vite.config.ts: ssr.external 排除 doubaoime-asr/opus-encdec，避免 require.resolve 路径失效
- scripts/post-build.ts: 简化为直接处理单文件 dist/cli.js
- src/services/doubaoSTT.ts: 改进错误信息，输出具体异常内容便于排查

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/services/doubaoSTT.ts

@@ -110,12 +110,15 @@ export async function connectDoubaoStream(
   let doubaoAsr: typeof import('doubaoime-asr')
   try {
     doubaoAsr = await import('doubaoime-asr')
-  } catch {
-    logError(new Error('[doubao-asr] Failed to import doubaoime-asr package'))
-    callbacks.onError(
-      'doubaoime-asr package is not installed. Install it with: bun add doubaoime-asr',
-      { fatal: true },
+  } catch (err) {
+    logError(
+      new Error(
+        `[doubao-asr] Failed to import doubaoime-asr package: ${String(err)}`,
+      ),
     )
+    callbacks.onError(`doubaoime-asr package import failed: ${String(err)}`, {
+      fatal: true,
+    })
     return null
   }