Add shift range text selection

[MoeidHeidari]

Description

Implements shift+click selection behavior in the terminal to allow extending selections from the current cursor position or existing selection.

Related Issue

Closes #205

Changes Made

• Added new SelectionMode.shift enum value to support shift+click selection behavior
• Implemented shift+click selection handling in TerminalGestureHandler
• Added keyboard event handling for shift key state tracking
• Improved selection direction handling to maintain consistent selection direction when extending selections
• Added proper handling of cursor position when no selection exists

Technical Details

• Added shift key state tracking using HardwareKeyboard events
• Implemented selection extension logic that:
  • Uses cursor position as anchor when no selection exists
  • Uses existing selection's start point as anchor when extending
  • Maintains selection direction (forward/reverse) when extending
• Added proper handling of selection modes (line, block, shift) in the gesture handler

Testing

• Tested shift+click selection with:
  • No existing selection (uses cursor position)
  • Existing selection (extends from selection start)
  • Different selection directions (forward/reverse)
  • Different selection modes (line/block)
• Verified selection behavior with:
  • Single clicks
  • Drag operations
  • Long press operations

Additional Notes

• No breaking changes
• Improves user experience by making text selection more intuitive
• Follows common terminal selection behavior patterns

[MoeidHeidari]

No update?

[MoeidHeidari]

I think the last commit should fix the issue in GitHub actions

[xtyxtyx]

Hi, first really thanks for your interest and effort in contributing to the project.

However while the code works, it has much room for improvement. For example most of the core logic in this PR is placed in a utility class TerminalGestureHandler, and the BufferRangeShift class is introduced without clear semantics.

If the code is generated by AI, please guide the AI to generate better-structured code and review it in person before submitting the PR.

Thanks!

[MoeidHeidari]

Thanks for the review

but I think if any part of the code has any semantic issue it was better if you would just comment on the code lines for me to fix instead of call it AI generated code when I spent hours to do an improvement and contribute.

Any way thanks for the review.