Drive splat orientation from DataTable.transform instead of per-format hardcoding

[slimbuck]

Summary

• Replace the hardcoded per-format getOrientation(filename) switch in asset-loader.ts with the transform returned by splat-transform's readers, so each format's authoring frame is described by data rather than baked into the editor.
• loadGSplatData now returns { gsplatData, transform }; the asset loader hands the Quat rotation straight to Splat.
• Splat's constructor takes a Quat and applies it via setLocalRotation, replacing the previous Vec3 Euler + setEulerAngles (avoids the deg→quat→deg round-trip and removes Euler ambiguity).

Why

The getOrientation switch returned (0, 0, 180) for PLY/splat/KSplat/SOG, (90, 0, 180) for LCC, and (0, 0, 0) for SPZ. Splat-transform already tags every DataTable with the correct authoring-frame Transform (PLY/splat/KSplat/SOG/SPZ → Transform.PLY = (0, 0, 180); LCC → (90, 0, 180)), so the per-format switch was duplicating information that the loader already provides — and the SPZ entry was wrong (this is what made SPZ files load 180° rotated relative to the equivalent PLY).

Compatibility

Requires @playcanvas/splat-transform with the SPZ coordinate-system fix (in flight at playcanvas/splat-transform#230). With that version, SPZ files load with the same (0, 0, 180) orientation as PLY and the two render identically.

Test plan

• Load a .ply scene — orientation matches previous behavior.
• Load the same scene as .spz — now orients identically to the PLY (was 180° around Y before).
• Load a .lcc scene — orientation matches previous behavior (90, 0, 180).
• Load .sog, .compressed.ply, .ksplat, .splat — all orient as before.

[Copilot]

Pull request overview

This PR changes how SuperSplat determines the initial orientation of loaded splat assets by using the authoring-frame transform provided by @playcanvas/splat-transform readers, instead of hardcoded per-format orientation logic in the editor. It also switches the Splat constructor to accept/apply a quaternion rotation directly to avoid Euler ambiguity and unnecessary conversions.

Changes:

• Removed per-format getOrientation(filename) logic and now drive orientation from DataTable.transform.
• Updated loadGSplatData to return { gsplatData, transform } and threaded that through the asset loader.
• Updated Splat to take a Quat and apply it via setLocalRotation instead of Euler degrees.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/splat.ts	Updates Splat construction to take/apply a Quat rotation (replacing Euler-based orientation).
src/io/read/loader.ts	Changes loadGSplatData to return both converted GSplatData and the source Transform.
src/asset-loader.ts	Removes hardcoded orientation switch and passes transform.rotation to Splat.

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[josetiburcio55-cpu]

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