Bind groups getting created while zooming / panning out

[0531769](https://github.com/GraphiteEditor/Graphite/commit/0531769c4181397aa0ad36bae25163cb878f42b3) (2026-02-22): Cache Vello render output as stitchable textures ([#3722](https://github.com/GraphiteEditor/Graphite/pull/3722))

Introduced in this commit , when you try to zoom in / out an image there are additional bind groups created which should not be the case . You can use this extension to checkout the bind groups getting created for firefox

https://addons.mozilla.org/en-US/firefox/addon/webgpu-inspector/

or for chrome

https://chromewebstore.google.com/detail/webgpu-inspector/holcbbnljhkpkjkhgkagjkhhpeochfal

Start by comparing commit 0531769, which introduced cached Vello render output as stitchable textures, and reproduce zooming or panning with the WebGPU Inspector extension. Trace the bind groups created during that interaction and confirm that zooming or panning no longer creates the additional groups shown in the report.

索引モデルが issue の本文から書いたものです。