Phayriosis Reborn Continued 0.0.19 - Phase 7B

Purpose:
Expand the proven Phase 7A Create World settings screen without disturbing the accepted meteor event or its SRP-style Create World button lifecycle.

Sections:
- Meteor
- Infection Difficulty
- Infection Config
- Advanced

Important compatibility bridge:
The original MCreator-era infection procedures still read PhayriosisrebornModVariables.MapVariables. Therefore the new-world profile writes its infection settings to both PhayriosisWorldSettings and MapVariables when the new world is first created. This prevents the new GUI from becoming a cosmetic-only settings layer.

Do not remove that bridge until all old infection procedures have been migrated to the new world-settings backend.
