Add native NeoForge 26.2 support via FFAPI

[Magi1053]

Summary

• Adds Plan/neoforge targeting Minecraft 26.2 / NeoForge 26.2.x, shipping a separate PlanNeoForge-*.jar (same pattern as Fabric).
• Reuses Fabric listeners/mixins/events through Forgified Fabric API; loader-specific entrypoint uses @Mod + FMLPaths.
• Wires CI artifact upload and Modrinth/CurseForge NeoForge publish stub.
• Stack bottom for Magi1053/Plan; upstream draft: Add native NeoForge 26.2 support via FFAPI plan-player-analytics/Plan#4811
• Tracks Native NeoForge support via Forgified Fabric API plan-player-analytics/Plan#4810

Notes

• FFAPI has no 26.2 release yet; build depends on FFAPI 0.155.2+26.1.2+3.5.0 as a stand-in until Sinytra publishes 26.2.
• Small Fabric sharing change: PlanPlugin is used where NeoForge shares Fabric listener/command types.

Test plan

• ./gradlew :neoforge:compileJava and :neoforge:shadowJar (Java 21+ Gradle JVM; toolchain 25)
• CI uploads PlanNeoForge-*.jar
• NeoForge 26.2 + FFAPI loads Plan; /plan works; sessions persist
• :fabric:shadowJar still builds