Test model for Sampler wrap modes and filters

I realized that there doesn't seem to be a _dedicated_ test model for the [`Sampler`](https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#reference-sampler) `magFilter`/`minFilter`/`wrapS`/`wrapT` configurations.

A suggested test:

Just a few squares with texture coordinates in (-1,1)-(2,2), using `REPEAT`, `MIRRORED_REPEAT`, `CLAMP_TO_EDGE`, once with `LINEAR` and once with `NEAREST`. (One could create dozens of combinations with different `wrapS`/`wrapT` and `minFilter`/`magFilter` modes, but I think that the given cases should cover everything already)

For quick tests, the asset as an _embedded_ glTF for now:

[SamplerModesTest 2026-06-11.zip](https://github.com/user-attachments/files/28839792/SamplerModesTest.2026-06-11.zip)

@emackey , @lexaknyazev If that makes sense, I'd wrap it up and add it as a sample.

Start with the attached embedded glTF asset, SamplerModesTest 2026-06-11.zip, and compare it with the repository's existing sample assets. Add a dedicated sample covering the stated REPEAT, MIRRORED_REPEAT, and CLAMP_TO_EDGE cases with LINEAR and NEAREST filtering; done means the asset clearly exercises these sampler configurations.

Written by the indexing model from the issue text.