Add a null check to query vis job runner to prevent crashes on disconnect.

Move useJobs into client code

merge from main

Add a QueryVisJobRunner to handle visibility checks in batches while also allowing for layer mask filters. Name tags are now a lot more stable with the magic offset removed and physics based visibility checks. Split the bot.crouch command into two client/server commands.

Add admin "bot.crouch" command to help test with nametag visibility testing.

merge from main

Fix player nametags being visible through ceilings: - We no longer use the name tag world offset for vis check, just the bone position on its own. - Use neck instead of the head bone to fix cases where the head is slightly clipping into the ceiling.