CobbleGacha Expanded v1.7.0 Alpha 3.6.4

50/50 guarantee rebuild:
- FIX: editor/custom reward banners now persist the actual featured-vs-off-rate 50/50 decision.
- FIX: losing a custom-banner Legendary 50/50 immediately sets the shared guaranteeGroup state.
- FIX: a guaranteed Legendary on another compatible banner in the same guaranteeGroup forces that banner's rate-up pool and consumes the guarantee.
- FIX: removed the redundant post-award guarantee writer that could act on stale banner/tier ThreadLocal context.
- FIX: the selected banner is canonicalized before rendering, clicking, and sending every pull, preventing stale banner indices after live rotation/sync changes.
- UI: the existing GUARANTEED NEXT LEGENDARY badge and rates-screen 50/50 status now read the same authoritative server state.
- guaranteeGroup=limited remains intentionally shared across limited banners.

Preserves Alpha 3.6.3 pity/editor/scheduler/large-UI features.
