Add Paper 26.2 compatibility

[briankeefe]

Summary

• bump squaremap's target Minecraft/platform versions to 26.2
• replace the Paper command manager construction with a small squaremap-specific Cloud Paper shim
• register only the Bukkit/Paper parsers squaremap uses, avoiding Cloud Bukkit's eager ItemStackParser initialization that crashes on Paper 26.2 due to the removed/changed CraftItemStack.asBukkitCopy(net.minecraft.world.item.ItemStack) reflection target

Verification

• ./gradlew --no-daemon :squaremap-paper:compileJava --stacktrace — BUILD SUCCESSFUL
• cd web && bun install; ./gradlew --no-daemon :squaremap-paper:build --stacktrace — BUILD SUCCESSFUL
• Disposable Paper 26.2 build 10 smoke test with built squaremap-paper-mc26.2-1.3.14-SNAPSHOT+442231a.jar — squaremap loaded and server reached Done; no CraftItemStack, ItemStackParser, or enable error appeared in server.log

Smoke test used a temporary server directory only; no live server/plugins were touched.

[drshockz]

Hey, I've got my own working version for 26.2. Do note Paper also updated Adventure libraries so that will also need updating here.

[briankeefe]

Closing this downstream compatibility workaround because the root fix landed upstream in Incendo cloud-minecraft: Incendo/cloud-minecraft#158. Once Incendo publishes a release/tag containing that merge, squaremap should be able to consume the dependency bump instead of carrying this local shim.