/vdt simulate now sees the same vetoes the engine applies

The memory safeguard and the chunk-generation lock both refuse a distance increase inside the check cycle, but neither existed in the preview /vdt simulate builds. On a server sitting under memory-safeguard.min-free-percent, the preview therefore announced an increase that the engine went on to reject — every cycle, with nothing to say why. Both now go through one shared method, so the reason the preview prints is the condition the engine acted on.

/vdt mspt has a permission of its own

It was the only subcommand falling through to the base /vdt node, while status, history and simulate each required one. It reads the same figures as /vdt status and now shares that node, so no existing grant changes meaning.

Smaller

• Removed a duplicate update.ahead key from messages.yml.
• plugin.yml now says that the reload permission also covers /vdt update.