debug(traceback): worker stderr 输出并按 fail-fast 注入 main

并行 worker 的 _vlog 不汇总；改为 stderr 直接输出 enabled/InstallSymbol；main 找不到 Install 时明确报错。

lib/Projectrans/Phase2Translator.py

@@ -2373,11 +2373,14 @@ class Phase2Translator:
                     if 'traceback' in str(_p):
                         _tb_sha1 = _k
                         break
+            trans.translator.TracebackEnabled = self.traceback_enabled
             if _tb_sha1 is not None:
                 trans.translator.TracebackInstallSymbol = f'{_tb_sha1}.Install'
-            _vlog().info(
-                f"[traceback] InstallSymbol={getattr(trans.translator, 'TracebackInstallSymbol', None)}"
-                f"  file={os.path.basename(src_path)}")
+            sys.stderr.write(
+                f"[traceback] file={os.path.basename(src_path)} "
+                f"enabled={self.traceback_enabled} "
+                f"InstallSymbol={getattr(trans.translator, 'TracebackInstallSymbol', None)}\n")
+            sys.stderr.flush()
         trans.SliceLevel = self.slice_level
         trans.translator.SliceLevel = self.slice_level
         trans.translator.SliceCount = 0