Fix mounted minecarts not persisting across world reloads

[ayushthoren]

Description

This PR fixes an issue where minecarts with riders would not spawn in properly upon loading a world.

Changes

Previous Behavior

If an entity was riding a minecart when the world was saved, reopening the world could leave the rider unmounted and the minecart missing. Minecarts without riders persisted normally.

Root Cause

Mounted minecarts were saved through the rider’s NBT data, but chunk entity loading only restored top-level entities and did not rebuild that chain.

New Behavior

When a world is reloaded, entities saved with mounts correctly restore their full riding chain, so ridden minecarts are present and still mounted.

Fix Implementation

Added riding chain reconstruction during chunk entity load in all relevant paths:

• OldChunkStorage::loadEntities
• LevelChunk::load
• ZonedChunkStorage::loadEntities

Each loader now goes through Entity::RIDING_TAG, loads each mount entity, adds it to the chunk, and links them properly.

AI Use Disclosure

I used AI as a tool to search for the chunk entity loading logic, then implemented the fix myself.

Related Issues

• Fixes [Bug] Minecart With Mob Despawning Upon World Load. #970

[rtm516]

Can we get addRidingEntities defined in LevelChunk? I've attached a patch to do this, or you can tick the box on the right to allow maintainers access to push to the PR

patch.diff.txt

[ayushthoren]

I have already given maintainers edit access, but I can apply the patch when I have time unless you get to it before me. :)

[rtm516]

Odd its giving me errors when trying to push. Ill let you apply it then ill get this merged.

error: Authentication error: Authentication required: You must have push access to verify locks