Inserting nucleotide between peptide in sequense causes adding nucleoside

[AlexeyGirin]

Steps to Reproduce

1. Go to Macro - Sequence mode (clean canvas)
2. Load from HELM: RNA1{R(A)P}|RNA2{R(U)P.R(U)}|PEPTIDE1{E.E}|RNA3{R(A)}$RNA1,RNA2,2:pair-2:pair|RNA1,PEPTIDE1,3:R2-1:R1|PEPTIDE1,RNA3,2:R2-1:R1|RNA3,RNA2,2:pair-5:pair$$$V2.0
   
3. Click between E symbols to switch to Edit mode
4. Press A key to insert RNA

Actual behavior
System inserts A nucleoside

Expected behavior
System inserts A nucleotide

Versions

• Ketcher Version 3.1.0-rc.2 Build at 2025-02-07; 15:09:23
• Indigo Version 1.29.0-rc.1.0-g2e30df8f7-wasm32-wasm-clang-19.0.0
• Chrome Version 133.0.6943.54 (Official Build) (64-bit)
• Win10

Issue found while testing: #5942