Automatic switching between light and dark theme (CSI 2031)

Related problem

Currently, nushell does not have support for switching between dark and light theme - there is always only one color theme configured in $env.config.color_config.

Several terminals (Ghostty, Contour, Kitty) have implemented support for CSI 2031 https://github.com/contour-terminal/contour/blob/f3c3334aa5c861348c5bbe8ffe572c872eef2e08/docs/vt-extensions/color-palette-update-notifications.md which allows terminal applications to receive updates regarding the current system theme, and then automatically switch between light/dark theme.

It would be nice if nushell had support for this.

Describe the solution you'd like

• Refactor current color theme configuration $env.config.color_config to support light and dark theme, e.g.:

env.config.color_theme = "light"
env.config.color_theme_light = ...
env.config.color_theme_dark = ...

• Implement support for CSI 2031 https://github.com/contour-terminal/contour/blob/f3c3334aa5c861348c5bbe8ffe572c872eef2e08/docs/vt-extensions/color-palette-update-notifications.md to receive information about current system theme.

Describe alternatives you've considered

No response

Additional context and details

No response

No files, tests, or entry points are named. Start by locating the implementation of $env.config.color_config and the terminal input handling relevant to CSI 2031. Done means light and dark theme configuration is supported and Nushell can receive CSI 2031 notifications to switch themes automatically.