Add 26.3 support

[im-a-bird]

Add Minecraft 26.3 support

Ports RedstoneTools to Minecraft 26.3. Coded with Claude's help and it built cleanly against the real 26.3 game jar / fabric-api / malilib.

Changes:

• Added the 26.3 stonecutter version target
• Fixed the Items.WHITE_SHULKER_BOX → Items.DYED_SHULKER_BOX.white() API change (dyed items got consolidated in 26.3)
• Fixed RedStoneWireBlock → RedstoneWireBlock rename
• Fixed Minecraft.screen moving to Minecraft.gui.screen()
• Rewrote the AirPlace block-outline renderer for 26.3's new submit-node rendering pipeline (LevelRenderContext.submitNodeCollector() replaces the old buffer/mixin-based approach)
• Excluded malilib-api's stale transitive malilib-fabric dependency pin so it resolves against the real installed version instead

Tested manually in-game on 26.3 (Fabric loader 0.19.5).

This was closed once already (#429) over two concerns, both addressed here:

• Readability of the denser branches: added explanatory comments to the AirPlace outline rendering and the now-empty invoker mixin, explaining what changed and why for each Minecraft version era.
• malilib-api still doesn't have a 26.3 build. Nothing here references malilib-api's internals directly beyond the one version property in versions/26.3/gradle.properties, so swapping in a real 26.3 build once it's published is a one-line change. Happy to hold this open until then, or update it myself once it lands.