#9889 - Errors are displayed after switching between Expand and Colla…

[PaulinaKacz]

This PR fixes a regression where structure errors could appear after collapsing/expanding monomer functional groups, switching between Macro and Micro modes, and then using Snake mode.

Problem
In specific workflows (especially multi-selection collapse/expand and Snake layout transitions), attachment-point/bond mapping could become inconsistent, which later produced structure validation errors.

Root Cause
1 Multi-selection expand/collapse was using monomer-specific logic that is safe for simple monomer topologies but fragile for complex/multi-group operations.
2 For monomers with more than 2 attachment points, monomer-specific expand/collapse logic could destabilize state after mode switches.
3 During Macro -> Micro conversion, attachment-point mappings could be missing/stale for some polymer and monomer-to-atom bonds.

Changes
1 Switched multi-selection context-menu handling to generic S-group expansion/collapse:
useMonomerExpansionHandlers.ts
useFunctionalGroupEoc.ts
2 Added fallback in monomer expand/collapse:
For monomers with >2 attachment points, use generic S-group logic instead of monomer-specific logic.
sgroup.ts
3 Hardened attachment-point synchronization before conversion:
Added synchronization for polymer bonds and monomer-to-atom bonds before converting drawing entities to Struct.
MacromoleculesConverter.ts
4 Fixed type/runtime consistency in converter import (required for instanceof checks):
MacromoleculesConverter.ts

Why this is safe
1 The behavioral change is targeted to risky paths:
multi-selection operations and high-attachment-point monomers.
2 Existing logic for single simple monomer expand/collapse remains unchanged.
3 Converter changes are defensive and only restore missing mappings when absent.
Tests Added
1 React regression test for multi-selection path:
Ensures multi-selection uses generic S-group expansion/collapse.
useFunctionalGroupEoc.test.ts
2 Core regression test for >2 attachment points:
Ensures fallback to generic S-group logic is applied.
sgroup.test.ts

Validation Performed
1 Unit tests:
useFunctionalGroupEoc.test.ts
sgroup.test.ts
2 Type checks:
packages/ketcher-core and packages/ketcher-react passed tsc --noEmit.
3 Manual verification:
Original user scenario reproduces correctly without structure errors.

Check list

• unit-tests written
• e2e-tests written
• documentation updated
• PR name follows the pattern #1234 – issue name
• branch name doesn't contain '#'
• PR is linked with the issue
• base branch (master or release/xx) is correct
• task status changed to "Code review"
• reviewers are notified about the pull request