Structure loaded in flex mode is horizontally flipped compared to snake mode

Found while testing #3600

**Steps to Reproduce**

1. Open Macromolecules (clean canvas)
2. Select Flex mode
3. Load from `HELM: RNA1{r(A)p.r(A)p.r(A)p}|RNA2{p.d(T)p.d(T)p.d(T)}$RNA1,RNA2,5:pair-6:pair|RNA1,RNA2,2:pair-9:pair|RNA1,RNA2,8:pair-3:pair$$$V2.0`
4. Switch to Snake mode
5. Compare the structure’s orientation in both Flex and Snake modes

**Actual Result:**
The structure displayed in Flex mode is horizontally flipped relative to its appearance in Snake mode

**Expected Result:**
The structure should be displayed with the same orientation in both Flex and Snake modes

**Found in Environment:**

- 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 148.0.7778.97 (Official Build) (64-bit)
- Win11