Lock envAtlas width and encoding for project

[luo2430]

No description provided.

[willeastcott]

Summary

This fixes a UI bug in the texture reprojection panel (src/reproject-panel.ts) where the width and encoding fields remained editable even when the target projection is envAtlas, which requires a fixed atlas format.

Before

When envAtlas was selected, onTargetProjectionChanged set encoding.value = '2' (RGBP) and width.value = 512, but left both fields editable. A user could then change them afterwards and generate a malformed atlas, since the engine's atlas generation relies on a fixed 512px layout for correct shader UV sampling and mip-grid alignment.

After

The fields are now disabled for envAtlas, locking them to the engine-required values:

width.enabled    = !isEnvAtlas;   // locked for envAtlas
encoding.enabled = !isEnvAtlas;   // locked for envAtlas

Also included

• Refactored the projection check (indexOf(...) === -1 → !...includes(...)) and extracted projection / isEnvAtlas locals for readability.
• Removed a redundant trailing null argument from a new Asset(...) constructor call.

Net effect: when reprojecting a texture to an env-atlas, the width and encoding controls are greyed out and pinned to the values the engine expects (512px / RGBP), so they can no longer be overridden into an invalid state.

[slimbuck]

tested, works. thanks for the pr!