Export to Extended SMILES works wrong for S-Groups

**Steps to Reproduce**
1. Open Molecules (clean canvas)
2. Load from KET: [Export to Extended SMILES works wrong for S-Groups.zip](https://github.com/user-attachments/files/28098824/Export.to.Extended.SMILES.works.wrong.for.S-Groups.zip)

3. Export canvas to Extended SMILES

**Actual behavior**
Export result: `C(CC)CCCCCCCCCCCC |Sg:n:1,2,3:1:ht,Sg:n:4,5,6:2:hh,Sg:n:7,8,9:3:eu|`

**Expected behavior**
Export result: `CCCCCCCCCCCCCCC |Sg:n:3,4,5:1:ht,Sg:n:6,7,8:2:hh,Sg:n:9,10,11:3:eu|`

**Environment details:**
- Ketcher Version 3.16.0-rc.1 Build at 2026-05-06; 20:39:57
- Indigo Version 1.44.0-rc.3.0-g5ef48a5af-wasm32-wasm-clang-23.0.0
- Chrome Version 148.0.7778.98 (Official Build) (64-bit)
- Win11

Related issue https://github.com/epam/ketcher/issues/2093