Sync mode causes incorrect letter input after adding a monomer in non-sync mode

[Zhirnoff]

Description:
When a user adds a monomer (U) in antisense with sync mode disabled, the antisense strand flips to the top during editing. After enabling sync mode and clearing the canvas, the letter input becomes reversed, meaning pressing "A" types "U" and pressing "U" types "A".

Steps to Reproduce

1. Open sequence mode and create sense and antisense chains.
2. Disable sync mode and add monomer "U" in the antisense chain.
3. Notice that the antisense strand flips during editing.
4. Enable sync mode and click Clear Canvas.
5. Try to type "A" or "U" on the keyboard.

Actual behavior
The letter input is reversed:
Pressing "A" types "U".
Pressing "U" types "A".

Expected behavior
Letter input should remain correct: pressing "A" should type "A", pressing "U" should type "U".

Video

2025-03-07_18h13_37.mp4

Desktop:

• OS: Windows 11
• Browser Chrome
• Version 133.0.6943.127 (Official Build) (64-bit)

Ketcher version
[Version 3.2.0-rc.1]
Indigo version
[Version 1.30.0-rc.1]
This bug was found while testing: #6254