Optimize GLTF instancing and outline rendering hot paths.

[RZDESIGN]

Reduce per-frame instance attribute uploads and scene churn, cache dynamic entity iteration, and prebuild outline mask material variants while skipping outline prep when no targets exist.

[RZDESIGN]

Reviewer checklist for this PR (GLTF/outline/entity hot paths):

• Validate instancing updates under movement/animation-heavy scenes: confirm reduced hitches and no stale instance data from dirty-range uploads.
• Validate transparent overlap quality: projected-depth sorting should improve ordering while remaining stable with throttled sort cadence.
• Validate outline rendering: no visual regressions for map/alphaMap combinations; ensure no extra work occurs when there are no outline targets.
• Validate entity update behavior: cached dynamic-entity iteration should preserve previous gameplay-visible update ordering.

Potential behavior change to confirm:

• Environmental entities inferred as StaticEntity remain non-removable/non-dynamic; verify this inference matches expected gameplay/server semantics.