fix Wayland ghosting using GL_TEXTURE_SWIZZLE_A

[nschimme]

Fix window ghosting artifacts on Wayland by forcing the alpha channel of the resolved FBO texture to 1.0, ensuring the final composition is fully opaque to the compositor.

Summary by Sourcery

Bug Fixes:

• Prevent window ghosting artifacts on Wayland by swizzling the resolved framebuffer texture alpha channel to 1.0 on non-WASM platforms.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Configures the resolved FBO texture so that its alpha channel is forced to 1.0 (except on WebAssembly), eliminating Wayland ghosting artifacts caused by non-opaque alpha being presented to the compositor.

Sequence diagram for updated FBO configuration and alpha swizzle

sequenceDiagram
    participant Functions
    participant FBO
    participant OpenGL

    Functions->>FBO: configure(getPhysicalViewport(), samples)
    Functions->>FBO: resolvedTextureId()
    FBO-->>Functions: textureId
    alt CURRENT_PLATFORM != PlatformEnum::Wasm and textureId != 0
        Functions->>OpenGL: glBindTexture(GL_TEXTURE_2D, textureId)
        Functions->>OpenGL: glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_SWIZZLE_A, GL_ONE)
        Functions->>OpenGL: glBindTexture(GL_TEXTURE_2D, 0)
    end

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File-Level Changes

Change	Details	Files
Force the resolved FBO texture alpha channel to 1.0 via GL texture swizzle to avoid Wayland window ghosting, with WebAssembly excluded.	Include computed config constants header so platform checks (CURRENT_PLATFORM) are available in this translation unit Extend Functions::configureFbo to, after configuring the FBO, fetch the resolved texture ID and if valid bind it and set GL_TEXTURE_SWIZZLE_A to GL_ONE, then unbind Guard the new texture swizzle logic with a compile-time check to skip it on the Wasm platform where WebGL2 does not support texture swizzling	src/opengl/legacy/Legacy.cpp

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[sourcery-ai]

Hey - I've left some high level feedback:

• Binding and unbinding GL_TEXTURE_2D inside configureFbo introduces a new side effect; consider saving/restoring the previously bound texture so callers’ GL state assumptions remain valid.
• The swizzle parameter is set every time configureFbo runs; if the resolved texture is reused across frames, you could guard this with a small flag or move it to the FBO/texture initialization path to avoid redundant state changes.
• The workaround currently applies to all non-Wasm platforms; if the ghosting issue is specific to Wayland, consider scoping this behavior behind a more precise platform/window-system check or configuration flag to avoid surprising behavior on other backends.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- Binding and unbinding GL_TEXTURE_2D inside configureFbo introduces a new side effect; consider saving/restoring the previously bound texture so callers’ GL state assumptions remain valid.
- The swizzle parameter is set every time configureFbo runs; if the resolved texture is reused across frames, you could guard this with a small flag or move it to the FBO/texture initialization path to avoid redundant state changes.
- The workaround currently applies to all non-Wasm platforms; if the ghosting issue is specific to Wayland, consider scoping this behavior behind a more precise platform/window-system check or configuration flag to avoid surprising behavior on other backends.

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 25.38%. Comparing base (7510a6b) to head (7bbafb4).

Files with missing lines	Patch %	Lines
src/opengl/legacy/Legacy.cpp	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #535      +/-   ##
==========================================
- Coverage   25.39%   25.38%   -0.01%     
==========================================
  Files         521      521              
  Lines       43178    43183       +5     
  Branches     4708     4709       +1     
==========================================
  Hits        10963    10963              
- Misses      32215    32220       +5     

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