CB-5506 support directional selections

[devnaumov]

The current implementation relies on from and to to represent the selection range in the editor. While this approach works for simple scenarios, it lacks the ability to properly handle selection direction and advanced cursor behavior. For example:

• Directional Selections: When a user selects text in reverse (e.g., moving left while holding shift), from and to fail to retain which side of the selection the cursor (caret) is on.
• Selection Extension: Keyboard shortcuts like cmd + shift + left require precise tracking of the fixed start (anchor) and current cursor position (head) to extend the selection correctly.