System should NOT save ambiguous amino acid to 1-letter sequence as X

[AlexeyGirin]

Steps to Reproduce

1. Go to Macro - Flex mode (clean canvas)
2. Load from HELM: PEPTIDE1{(A,C)}$$$$V2.0
   
3. Save canvas to 1-letters Sequence

Actual behavior
System saves it as X

Expected behavior
Error message should occur

as per requirement:

2.3. If one of the amino acids is a non-standard ambiguous amino acid an error message should appear, with the title "Non-standard amino acid" and text "Non-standard ambiguous amino acids cannot be exported to the selected format".

By standard ambiguous amino acids we consider amino acids that we have in the library (B, J, X, and Z).

Versions

• Ketcher Version 3.2.0-rc.1 Build at 2025-03-04; 14:24:35
• Indigo Version 1.30.0-rc.1.0-g9bdedaba9-wasm32-wasm-clang-19.0.0
• Chrome Version 134.0.6998.36 (Official Build) (64-bit)
• Win10

Issue found while testing: epam/Indigo#2015