[xen2]

PR details

Fixes the GPU hang reported on Discord when switching a material to tessellation in Game Studio ("The GPU device instance has been suspended", DriverInternalError).

While the new effect compiles, the editor draws with a fallback effect that has no hull shader, but the mesh has already switched to the tessellated patch list. That draw is invalid (D3D11 debug layer: "input topology is Patch Control Points... You need either a Hull Shader and Domain Shader") and hangs the driver on real hardware.

• MeshRenderFeature: a render node whose effect is compiling or errored draws the original mesh instead of the tessellated draw. The fallback stays a plain, shared permutation that never depends on user shaders.
• MeshFallbackEffects: the fallback material and parameter setup moved from the editor into Stride.Rendering, so the engine test runs the real thing. The editor only adds its compiling/error glow flags.
• EffectFallbackTest: a gated compiler holds back the tessellated permutation for one frame, so the fallback path runs on every GPU lane. It crashes without the fix.
• Effect: found by the test on a warm effect cache. Deserialized bytecode holds a resource group's cbuffer and the matching ConstantBuffers entry as two instances, and only the second one was hashed. All cached effects with the same descriptor layout then shared one PerView/PerFrame layout, with the size and member offsets of whichever effect came first. Both instances are hashed now. 4.4 only, and invisible on CI because CI always runs cold.