… layers

# Objective

olor emoji (COLR glyphs) are rasterized on the GPU by compositing each
glyph layer into a D3D11 render target that is created with
`pInitialData: None` and, until now, never cleared. The texture contents
are undefined: texels not covered by any layer quad retained garbage
(typically leftovers from previous rasterizations via the DXGI
allocation pool).

## Solution

- Clear the render target with `[0, 0, 0, 0]` (premultiplied
transparent) immediately after binding it and before drawing the layers.

## Testing

add test to test this specifically 


## Showcase

before : 
<img width="1634" height="754" alt="ezgif-1a339c7dea79f905"
src="https://github.com/user-attachments/assets/6e282c46-d2a4-4043-9c1c-7f4ee9232fcc"
/>


after : 

<img width="1677" height="690" alt="Screenshot 2026-08-26 015248"
src="https://github.com/user-attachments/assets/c922909e-c70b-49f0-88fd-5a0c7cbe574b"
/>

---

Release Notes:

- Windows: Fixed artifacts around color emoji glyphs