New HudGroups autoload manages show/hide of related HUD elements as
groups. Exclusive groups (gameplay, implant) are mutually exclusive —
opening the star map hides stance indicator, minimap, interaction
prompts, etc. Closing it restores them.
Gameplay nodes registered in main.gd _ready(). Star map registers as
implant group and uses toggle_group() instead of direct visibility.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>