- portals.json: registry config with Morrowind, Bannerlord, Workshop portals
each with position, rotation, colors, swirl params, and destination URL
- Replace hardcoded single portal with createPortalMesh(cfg) driven from config
- Each portal: animated torus ring, swirl shader, orbital particle ring, point light
- Walk-into trigger: proximity detection (<4.5 units) shows F-key hint HUD
- Click trigger: raycasting on canvas click activates nearest portal ring
- Portal overlay: shows name, description, status with countdown if URL set
- Drag guard prevents accidental portal activation during mouse-look
Fixes#5
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>