Make Realm Explore lists collapsible

[ael-dev3]

Summary

• add independent disclosure controls for Castles, Workers, Resource Sites, and Public Water in Realm Explore
• show live filtered/total counts, keep section controls sticky, and contain overscroll in the single Explore scroll surface
• preserve expanded state across hosted Back navigation and automatically reopen sections with search matches
• keep native buttons, stable aria-controls targets, one aggregate search announcement, and reduced-motion-safe chevrons

Why

Long Realm inventories can force Mini App users to scroll through hundreds of rows before reaching another category. These controls let players collapse any list without removing search, community, view, or coordinate actions.

Validation

• 3,001 Vitest tests across 269 files
• TypeScript project build
• Vite production build
• runtime/provenance asset verification
• production output and Farcaster Mini App integrity verification
• license and tracked file-size policies
• independent accessibility review

[ael-dev3]

Fully subsumed and bounded by #195 / main 98a3636. The collapsible Explore lists are present with later inventory limits; this draft must not be merged separately.