WebGPURenderer: Track frontFaceCW in needsRenderUpdate.

[LLiJJing]

Description

Fixes #33779.

WebGPUBackend.getRenderCacheKey includes frontFaceCW = object.isMesh && object.matrixWorld.determinant() < 0 in the pipeline cache key because the GPU frontFace enum is baked into the pre-compiled render pipeline. However, the sibling WebGPUBackend.needsRenderUpdate doesn't track the same signal, so when an existing mesh transitions between positive and negative determinant (typical case: editor toggles a mirror/flip via negative scale on an axis), Pipelines.getForRender short-circuits on the cached renderObject.pipeline and never re-evaluates the cache key. The mesh continues to draw with the stale frontFace, culling the visually-outward fragments. For lit opaque materials this results in a fully-black render.

This PR adds frontFaceCW to needsRenderUpdate's dirty check so the two sides of the cache surface stay symmetric.

Reproduction

See linked issue for the JSFiddle live demo (https://jsfiddle.net/fvpbt90h/23/). Before this patch, clicking "flip" causes the TorusKnot to disappear (closed convex geometry → all faces culled by stale frontFace) and clicking "workaround" makes it reappear. After this patch, "flip" works correctly on its own without needing the manual material.needsUpdate = true bump.

Notes

• Two-line addition mirroring the shape of every other comparison in needsRenderUpdate.
• Zero behavioural change for objects whose matrixWorld.determinant() never changes sign — the new comparison just stores a stable false (or stable true) in data.frontFaceCW.
• The first frame after a sign change pays one extra pipeline cache lookup; subsequent frames at the new sign hit the cache as before.
• npm run lint and npm run test-unit (1308 pass / 0 fail) both clean locally.
• Related historical fix in WebGLShadowMap along the same lines: Fix: wrong face cull for shadows of freshly inserted mirrored objects. #15825.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	365.5 86.83	365.5 86.83	+0 B +0 B
WebGPU	666.47 184.38	666.55 184.4	+77 B +24 B
WebGPU Nodes	664.51 184.07	664.59 184.09	+77 B +21 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	507.46 123.35	507.46 123.35	+0 B +0 B
WebGPU	745.72 200.58	745.8 200.6	+77 B +23 B
WebGPU Nodes	694.94 188.02	695.02 188.04	+77 B +22 B

[Mugen87]

I can confirm the bug is real and that your suggested fix solves the problem. This makes the WebGPU backend in line with the WebGL backend which does not have this issue since the check is already honored correctly.