Port Flywheel and Vanillin to Minecraft 26.2

[doscarchase]

Summary

• Port Flywheel and Vanillin to Minecraft 26.2 / NeoForge 26.2.0.8-beta.
• Move CI/toolchain to Java 25 and Gradle 9.6.1.
• Retarget rendering, model, lighting, and mixin integration to the 26.2 client APIs.
• Fix the sky-light storage mixin target to use the JVM inner-class name for SkyDataLayerStorageMap.
• Keep player uniforms off the LocalPlayer type so server-side class scanning does not probe client-only player classes.
• Decode Flywheel blue-noise textures as RGBA so Minecraft 26.2 DynamicTexture uploads do not fail on LUMINANCE image data during client resource reload.

Maintainer Note

• The release plan calls for upstream 26.2/dev to be created from 26.1.2/dev before merge.
• This account cannot create upstream branches (403), so this PR is opened against 26.1.2/dev and should be retargeted to 26.2/dev after maintainers create it.

Validation

• ./gradlew :neoforge:publishToMavenLocal :vanillinNeoForge:publishToMavenLocal --offline --stacktrace --no-daemon --console=plain -> BUILD SUCCESSFUL in 58s
• Downstream Create runData/runGameTestServer no longer report the missing Flywheel SkyDataLayerStorageMap target warning.
• Downstream Create client bootstrap no longer reports Caught error loading resourcepacks from Flywheel NoiseTextures.

Release Train

• Publish official flywheel-neoforge-26.2, flywheel-neoforge-api-26.2, and vanillin-neoforge-26.2 artifacts before Ponder/Create consume them.

[IThundxr]

Please do not make AI generated porting PRs, and 26.2 is already underway on my fork