Fix Paper 26.1.1 startup compatibility

[Riqqqque]

Summary

• update the Spigot command dependency stack for Paper 26.1.1 startup compatibility
• align the shared Java target with the newer dependency requirements

Root Cause

Paper 26.1.1 changed the underlying ItemInput handling used by Incendo Cloud's Bukkit/Paper item parser. Geyser's older shaded Cloud dependency still looked for the removed createItemStack path, which caused plugin startup to fail during command manager initialization.

Impact

This removes the Paper 26.1.1 startup crash so the Spigot plugin can load again on current builds.

Validation

• ./gradlew.bat :spigot:shadowJar
• ./gradlew.bat :spigot:runServer --console=plain on Paper 26.1.1 build 29 with Java 25

[SleepyPopp]

Thank you for the PR! However, there is a Geyser preview build available for Java 26.1.

Additionally, if your going to utilize AI to contribute to GeyserMC projects, please see our AI policy: https://github.com/GeyserMC/.github/blob/master/AI_POLICY.md

Experimental Geyser Preview Build:

• Geyser: Feature: 26.1, API 2.10.0 #6271

[Novampr]

As sleepy said, we already have a PR for this which adds full 26.1 compatibility, the PR is appreciated nonetheless :)