Flywheel OIT Fix

Initial release.

Fixes Create's Flywheel-instanced models rendering massively overbright under shaders.

Flywheel routes ORDER_INDEPENDENT materials through a separate accumulation buffer and resolves
them in a composite pass. Under iris-flywheel-compat that composite never runs, so unresolved
accumulation reaches the screen — shafts and cogwheels come out as blown-out white shapes.

This reports those materials as OPAQUE while a shaderpack is in use, sending them down the
ordinary draw path. Without a shaderpack nothing changes.