Hardcore: Gamemode and cheats can be enabled in world options after death

In Hardcore single-player world, players can turn on cheats and switch all gamemodes directly inside world options menu without opening to LAN; after dying and entering Spectator mode, users still can modify world settings to enable cheats or alter gamemode, revive and continue playing, completely invalidating hardcore's permanent world lock after player death.

Steps to Reproduce：

1. Launch vanilla Minecraft 26.2 Pre4, create a brand new single-player Hardcore world (no pre-existing world edits, no mods).
2. Enter the newly created hardcore world, press Esc to open game pause menu.
3. Click Options → World Options inside pause screen.
4. In world options panel: toggle Allow Cheats ON, freely switch between Survival/Creative/Adventure/Spectator gamemode directly via options.
5. Make player character die in-game, select Spectate World on death screen to enter spectator mode.
6. Open pause menu again → Options → World Options once more.
7. Either turn on cheats to run  /gamemode survival  command, or directly change gamemode in world options, revert back to survival and keep playing the hardcore world normally.

Expected Result：

1. Hardcore world should lock Allow Cheats option and all gamemode selection inside World Options menu, all relevant switches greyed out and uneditable.
2. After player death in hardcore, once entering spectator mode, world settings must be fully locked; no way to enable cheats or modify gamemode, world should be permanently unplayable as hardcore rule defined.

Observed Behavior：

World Options menu keeps full edit permissions in living hardcore and post-death spectator state: cheats can be enabled anytime, any gamemode can be switched freely, users bypass hardcore permanent death penalty easily and continue progression.