Adding `-` between sense monomer connected via H-bond and sence monomer not connected cuts hanging antisense monomer away and doesn't show it on the canvas as new sequence

[AlexeyGirin]

Steps to Reproduce

1. Go to Macro - Sequence mode (clean canvas)
2. Copy the following HELM string to the clean canvas: RNA1{R(A)P.R(A)}|PEPTIDE1{D.D}|RNA2{R(U)P.R(U)}$PEPTIDE1,RNA1,2:R2-1:R1|RNA1,RNA2,5:pair-2:pair$$$V2.0
   
3. Click between the two A monomers to place the text caret. Make sure SYNC is ON. The SYNC icon must be dark blue, indicating the mode is active (not just enabled).
   
4. Press the “-” (hyphen) key on the keyboard while the caret is visible.

Actual behavior
System cuts the hanging antisense monomer away and doesn't show it on the canvas as a new sequence (small “p” appears before the U, no new monomers appear), and the detached monomer becomes visible only after exiting edit mode by clicking on the canvas.

Expected behavior
System cuts hanging antisense monomer away and shows it on the canvas as new sequence
System cuts the hanging antisense monomer away and shows it on the canvas as a new sequence (small “p” (phosphate) appeared before the U, new U monomer appeared below) immediately after pressing “-”, without requiring exit from edit mode.

Versions

• Ketcher Version 3.2.0-rc.4 Build at 2025-03-25; 16:50:39
• Indigo Version 1.30.0-rc.4.0-g552c98211-wasm32-wasm-clang-19.0.0
• Chrome Version 134.0.6998.178 (Official Build) (64-bit)
• Win10

Issue found while testing: #6254

[SefaBilgii]

This issue is reproducible

Screen.Recording.2025-07-31.at.7.00.00.PM.mov

Ketcher Version: 3.6.0-rc.1
OS: MacOs Sequoia Version 15.5
Browser : Chrome Version 138.0.7204.169

[AlinaLysenko]

Reproduced by agent - https://chatgpt.com/share/691ba210-2e1c-800e-90bf-b7681a49aabd