Eliminate all edge cases where Gemini CLI tries to be too much of a TUI app degrading the CLI experience

[jacob314]

When not in alternate buffer mode, Gemini CLI must behave as much like a standard terminal program rather than a TUI. Alternate buffer mode should provide an excellent TUI experience freeing the regular mode to provide an excellent terminal app experience with less TUI like garbage getting in the way of the experience of users who just want to type commands in the terminal. At the same time it is crucial the alternate buffer mode and regular modes do not diverge too much and we should land all features needed into Ink to avoid that. For example, we will add ink features to support "scrollable" boxes where the scrolled content gets added to the backbuffer when safe to add. This will enable the same UI structure with both a backbuffer based version for regular mode and a fully TUI mode when in alternate buffer mode with mouse support.

This means that things like copy and paste should work seamlessly without copying and pasting ascii line art, the terminal backbuffer is never cleared unexpectedly unless the user has resized the terminal, and the amount of output rendered is kept under control unless the user explicitly requests to expand large outputs.