Bug Fix: Cursor Support in Score Editor

🛠️ What Was the Issue?
Previously, the Score Editor only allowed users to delete from the end of expressions. This made mid-expression edits frustrating and time-consuming because users had to erase everything after the target position just to make a simple change.
✅ What’s Fixed
We’ve resolved this by introducing full cursor support, enabling precise editing at any position within an expression.
🔍 Key Fixes & Improvements
Click-to-Position:
 Users can now click anywhere in an expression to place the cursor.
Keyboard Navigation:
 Use arrow keys, Home, and End for smooth in-line movement.
Direct Input:
 Type numbers, operators, and parentheses directly at the cursor’s position.
Smart Insert/Delete:
 Edits happen exactly where the cursor is—no more forced end-only changes.
Visual Feedback:
 A blinking cursor, hover effects, and focus indicators make editing clear and intuitive.