Preview: System should not layout micro molecules even if they are selected

**Steps to Reproduce**
1. Open Macromolecules - Flex mode (clean canvas)
2. Load following ket file: [System should not layout micro molecules even if it is selected.zip](https://github.com/user-attachments/files/23187963/System.should.not.layout.micro.molecules.even.if.it.is.selected.zip)

3. Select all and call Layout

**Actual behavior**
System lays out everything including micro molecule

**Expected behavior**
System lays out everything except micro molecule

As per [requirement](https://github.com/epam/ketcher/issues/7970):
> 1.3. The closed structure must not include small molecules.

**Environment details:**
- Ketcher Version 3.9.0-rc.3 Build at 2025-10-22; 18:19:06
- Indigo Version 1.37.0-rc.2.0-gef86e7136-wasm32-wasm-clang-19.0.0
- Chrome Version 141.0.7390.123 (Official Build) (64-bit)
- Win10

Related issue: https://github.com/epam/ketcher/issues/7970

Reproduce the problem in Macromolecules - Flex mode with the attached KET file, select all, and call Layout. Compare the result with the expected behavior and requirement issue 7970; done means the selected micro molecule remains unchanged while the other structures are laid out.

Written by the indexing model from the issue text.