feat: Guard sky-limit block updates against out-of-range chunk section indices

[Copilot]

On 1.8, joining near the sky limit could crash MCC with an out-of-bounds exception while terrain updates were being applied. The failure came from treating the first invalid section above the world ceiling as if it were still inside the loaded chunk column.

• Root cause

  • World.SetBlock() accepted location.ChunkY == column.ColumnSize.
  • In 256-high worlds, Y=256 maps to chunk section 16, but valid sections are 0..15.
  • A block update at that boundary could therefore index past the chunk column.

• Change

  • Tightened the chunk-section bounds check in World.SetBlock().
  • The method now ignores block writes whose computed chunk Y is outside the valid column range, including negative section indices.

• Effect

  • Prevents terrain-update crashes at the upper world boundary.
  • Keeps normal in-range terrain handling unchanged.

ChunkColumn? column = this[location.ChunkX, location.ChunkZ];
if (column is not null && location.ChunkY >= 0 && location.ChunkY < column.ColumnSize)
{
    Chunk? chunk = column.GetChunk(location);
    if (chunk is null)
        column[location.ChunkY] = chunk = new Chunk();
    chunk[location.ChunkBlockX, location.ChunkBlockY, location.ChunkBlockZ] = block;
}

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• snoop.minecraft.net
  • Triggering command: /usr/bin/java /usr/bin/java -Xmx2G -Xms2G -jar server.jar nogui (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)