Port to 26.1 Fabric via Stonecutter

[cassiancc]

Proof of concept since you were open to the idea of a multiloader Block Box rather than a standalone Refabricated port from our team. There's a hundred ways to do this, I've opted for my favourite, which keeps dependencies and differences from the NeoForge version to a minimum.

• Ports mod to Stonecutter, a multiloader library designed to keep code in a single sourceset rather than managing platform specific subdirectories. Stonecutter uses versioned comments to handle multiloader code, and the active version can be switched via Gradle or IntelliJ tasks. The template I used comes with auto-publishing setup should you wish to try it.
• Ports mod to 26.1 Fabric
  • Added stubs for NeoForge events, data maps, and Item Abilities based on the convention tags, similar to the approach used in Farmer's Delight Refabricated
  • Removed use of legacy JavaX nullability annotations in favour of Mojang-preferred JSpecify annotations. JavaX annotations are entirely removed on Fabric.
  • Forge Config API port is a dependency on Fabric in order to keep changes to the NeoForge side as minimal as possible.
• Adds a CommonTags class for convention tags, rather than using NeoForge's Tags directly.
• Block registration now uses RegisterEvent rather than Deferred Registers.
  • Palisades now use registry checks rather than defining blocks in the constructor - this was incompatible with non-deferred registration, might be reworked later should this PR be of interest.