Port MEGA Cells to Minecraft 26.1.2 (4.12.0)

[ColinMoulds]

Summary

Ports MEGA Cells to Minecraft 26.1.2 and prepares version 4.12.0.

• update the build to Java 25, NeoForge 26.1.2.80, and AE2 26.1.10-beta
• migrate core code to the Minecraft, NeoForge, and AE2 26.1 APIs
• retain the Cell Dock, Portable Cell Workbench, Decompression Module, lava transforms, crafting multiblock rendering, capabilities, and crafting-unit behavior
• migrate recipes, recipe advancements, item definitions, part descriptors, block-state models, data maps, and bundled resource-pack metadata to the 26.1 formats
• restore compression override data-map registration and cover it with tests
• update the release workflow for Java 25 and Minecraft 26.1.2
• set the development/release artifact version to 4.12.0

Compatibility

Applied Flux support remains enabled for its available 26.1 release. Source and recipes for optional integrations whose dependencies do not yet provide 26.1 builds are excluded from the release JAR and marked unavailable in-game.

Why

Minecraft 26.1, NeoForge 26.1, and current AE2 releases changed persistence, networking, rendering, item-model, recipe, advancement, data-map, capability, and client registration APIs. The previous 1.21.1 code and generated resources therefore could not compile or reload correctly on 26.1.2.

Validation

• ./gradlew spotlessApply build passes
• all 9 unit tests pass
• client startup completes a full resource reload with no MEGA Cells warnings or errors
• packaged JAR contains 110 item definitions, 98 active recipes, 128 recipe advancements, the compression data map, and four AE2 part descriptors

[ColinMoulds]

@62832 Would you be open to creating a dedicated 26.1 branch and retargeting this PR to it?
This port includes breaking changes across Minecraft, Java, NeoForge, AE2, rendering, persistence, recipes, advancements, data maps, and item models. Keeping it on a separate version branch would allow the existing 1.21.1 codebase to continue receiving fixes without mixing incompatible changes.

It would also provide a place to stabilise the 26.1 port and restore optional integrations incrementally as their dependencies become available. Once 26.1 is considered stable, the branch could become the primary development line if desired.