Slabbed

For Minecraft 1.21.1 on NeoForge 21.1.233 or newer. Requires Java 21.

IMPROVED

• Chunk section rebuilds reuse checks for static columns. In a focused moving-light test, the section compiler used about 30% less CPU than in 0.6.7-alpha. Frame timing stayed close in that test. This is a partial improvement for #92. Thanks to sewzrat for reporting the lag.
• Ordinary chunk rendering and the tested Relatively Placed Blocks composite kept their seam faces through a resource reload. Diagnostic cases that force nested model wrappers or a fallback context can still lose faces. Other renderer paths remain unverified.