System doens't assing added bonds to defined Preset component

[AlexeyGirin]

Steps to Reproduce

1. Open Molecules (clean canvas)
2. Load from SMILES: CCCCCC

3. Select whole structure and press Create a monomer button to open Monomer creation wizard
4. Select "Nucleotide (preset)" type and define Base, Sugar, and Phosphate as shown on the screen below:

5. Go to Sugar tab 6. Select Single bond tool 7. Click on left edge Sugar atom

Actual behavior
System adds bond but it remains unassigned to Sugar component

Expected behavior
System adds bond and assigns it to Sugar component

As per requirement:

Additions to the structure

2.3. Every addition to the structure after components are defined, gets assigned to a component that it is connected to.

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

Found while tested #8852