The "Arrange as Ring" feature does not work correctly if there are multiple structures on the canvas.

**Steps to Reproduce**
1. Open Macromolecules
2 Open ket file [ExampleForN.zip](https://github.com/user-attachments/files/26897334/ExampleForN.zip)
3. Select FLEX mode > Select part of structure as bellow

4. Select Arrange as a Ring - it's OK

5 Press UNDO
5. Open the same file as second structure
6. Select the same part of structure in the any structure

7. Select Arrange as a Ring

**Actual behavior**
The "Arrange as Ring" feature does not work correctly if there are multiple structures on the canvas.
All structure Arranges as Rings.

**Expected behavior**
The "Arrange as Ring" feature should change only selected part of structure.

Please see record of the issue

https://github.com/user-attachments/assets/322bf004-f75f-4695-a40a-1e2a594d3484

Cyclic layout implemented in https://github.com/epam/Indigo/issues/3196
Found with issue https://github.com/epam/Indigo/issues/3605

Environment details:
[Version 3.15.0-rc.1](https://lifescience.opensource.epam.com/ketcher/index.html) Build at 2026-04-02; 15:41:30
[Indigo Toolkit](http://lifescience.opensource.epam.com/indigo/) Version 1.43.0-rc.1.0-gd74653443-wasm32-wasm-clang-19.0.0
• Chrome Version 144.0.7559.112 (Official Build) (64-bit)
• Win11

Reproduce the issue in Macromolecules using ExampleForN.zip, FLEX mode, two structures, and Arrange as a Ring; compare the behavior with the single-structure case. Review the cyclic layout context from issue 3196 and the related issue 3605. Done means only the selected part of the selected structure is rearranged while the other structure remains unchanged.

Written by the indexing model from the issue text.