Fix packed icons, CJK labels, and radial stalls

[lanxuy]

Summary

• resolve required icon assets directly from the packed Data0 archive when the runtime VFS does not expose them
• preload only equipped spell and item icon atlases outside the open-menu path
• merge Microsoft YaHei CJK glyphs into the overlay font and keep label truncation UTF-8 safe
• avoid per-frame retries after an empty radial open and invalidate slot caches when equipped IDs change

Closes #1

Validation

• git diff --check
• GitHub Actions build passed on the fork
• manual in-game validation with localized spell names and matching icons

No generated game assets or local diagnostic output are included.