Fix "Group 'vip' doesn't exist" (Oxide permissions)

Oxide keeps groups in its own data, separate from the plugin files. oxide.group add <name> creates that entry; oxide.usergroup add <player> <name> only links an existing player to an existing group. If you run the usergroup command first, or type the group name differently from how it was created, Oxide cannot find a group with that name and prints Group '<name>' doesn't exist. The same message appears when you grant a permission to a nonexistent group with oxide.grant group <name> <perm>. This is common on fresh servers where a plugin's docs list perms like vip.kit but nobody ran oxide.group add vip, and after wiping oxide/data (where the group list lives) while keeping a startup script that still assigns players to the old groups. Group names are case-insensitive, but a typo anywhere else in the name still fails.

1. Confirm which groups exist by running oxide.show groups (and oxide.show group vip to inspect one).
2. Create the group if it is missing: oxide.group add vip. Optionally pass a title and rank, e.g. oxide.group add vip "VIP" 1.
3. Add the player using their exact name or SteamID64: oxide.usergroup add 76561198000000000 vip.
4. Verify with oxide.show user 76561198000000000 — the output lists the player's groups — or oxide.show group vip, which lists members.
5. If the assignment is done by a plugin at startup, reorder it so the group is created before players are added, or create the group once by hand and keep it in a startup batch file that runs oxide.group add before oxide.usergroup add.
6. Repeat for each group your plugins reference. After the group exists, the earlier usergroup command can be re-run and will succeed without any reload.