chore(📚): small documentation fixes

[wcandillon]

Small fixes found while reviewing apps/docs.

• warnIfNotHardwareAccelerated: both examples called it on top of useDevice / GPUDeviceProvider, which already call it. The usage now says so and shows the manual requestAdapter() case.
• API overview: the "What this reference covers" list was missing Video Player and drawElementImageToTexture, and didn't point to GPUOffscreenCanvas, importDevice or adoptTexture.
• Offscreen Canvas: document what getImageData() resolves with, and that width must be a multiple of 64 (rows are copied without padding, and WebGPU requires bytesPerRow to be a multiple of 256).
• Three.js: the r184 leak callout explains the symptom and the workaround without RenderObjects / QuadMesh internals.
• React Three Fiber: the model-loading tip pointed to the Expo page, which says nothing about it; now it links to Three.js → Loading assets.
• TypeGPU: the Skia link used shopify.github.io; every other page uses wcandillon.github.io.