feat: add Chinese UI, Responses models, and mirrored Windows setup

Localize the web console and persist custom model and capability settings.
Use OpenAI Responses exclusively and move runtime limits into environment configuration.
Bootstrap uv and the virtual environment on Windows, support optional China mirrors,
and package source distributions without environments, build output, or credentials.

Update regression tests and repository quality checks for the new behavior.

start-cn.bat

@@ -0,0 +1,6 @@
+@echo off
+rem Use China mirrors for first setup and subsequent launches.
+rem All start.bat arguments, including -SetupOnly, are supported.
+setlocal DisableDelayedExpansion
+call "%~dp0start.bat" -Mirror China %*
+exit /b %ERRORLEVEL%