TUI: revisit mouse support after stabilizing the input model

[rmanibus]

Summary

Basic mouse support was explored and rolled back because it made input handling unstable.

We should revisit mouse support only after the current keyboard/input model is solid enough to support it cleanly.

Scope

• Reassess terminal input handling requirements for mouse support
• Reintroduce click-to-select only if it does not destabilize keyboard input
• Consider wheel navigation only after basic click behavior is reliable
• Keep portability across terminals in mind
• Add focused tests if mouse support returns

Why

• Mouse support can improve usability, but it should not compromise core interaction reliability
• This should be treated as a later enhancement, not mixed into unrelated TUI work

Related: #132, #211