Split geometry displays incorrect color when editing unsaved feature

Nobody has claimed this yet.

**Description**
When a new polygon/multipolygon feature is recorded and the user proceeds directly to Edit geometry without saving first, splitting the geometry results in the split part being displayed in an incorrect color (yellow) instead of the symbology color configured for the layer.

**Environment**
[ x ] Staging [

**Application (+ app version, build, operating system)**
Mergin Maps iOS 2025.6.0 / iOS 26.0 / iPhone 15

**Steps to reproduce**
1. Open a project with a polygon or multipolygon layer with a custom symbology color defined
2. Tap the Add button and select the polygon/multipolygon layer
3. Tap on the map to create a polygon geometry
4. Tap Record to confirm the geometry — **do not save the feature**
5. Immediately tap Edit geometry
6. Use the Split tool to split the geometry
7. Save the result

**Actual results**
The split part of the geometry is displayed in yellow, not in the layer's configured symbology color.

**Expected results**
Both parts of the split geometry are displayed in the symbology color configured for the layer.

**Screenshots or logs**

https://github.com/user-attachments/assets/78652a59-060d-4f28-99e6-ce9e2711a495

*Conclusion*
*Created by Claude and supervised by a human test analyst.*

Start by reproducing the issue through Add, Record, Edit geometry, and the Split tool on an unsaved polygon or multipolygon with custom layer symbology. Trace how the geometry editor assigns colors before and after splitting, then verify that both saved parts use the configured layer color rather than yellow.

Written by the indexing model from the issue text.