Method SetDebugFlatColor

engine/Poseidon/Graphics/Core/Engine.hpp:414–414

Diagnostic: replace object shading with a flat solid colour (red), keeping the alpha-test silhouette + cutout holes. A highlight that vanishes under flat colour is a shading/texture artifact; one that persists is a geometry/vertex-position artifact. No-op on backends that don't support it.

    // flat colour is a shading/texture artifact; one that persists is a
    // geometry/vertex-position artifact.  No-op on backends that don't support it.
    virtual void SetDebugFlatColor(bool /*enable*/) {}
    virtual bool GetDebugFlatColor() const { return false; }

    // SSAA render scale: render the frame at scale x window size into an