feat(playground): real 3D walkable world with iso camera, NPCs, portal

Eric: yes ship Fortnite Creative for Hermes agents. v0 is single-player
3D, v1 will add multiplayer + chat.

Adds @react-three/rapier and ecctrl deps and a new
PlaygroundWorld3D component that mounts:
- iso camera locked to player
- ecctrl character controller (WASD walk, Space jump, physics)
- ground + grid + classical or tech pillars per world
- center medallion accent ring
- 4 NPC billboards in Agora (Athena, Apollo, Iris, Nike)
- 2 NPC billboards in Forge (Pan, Chronos)
- glowing rotating portal that sensor-triggers world swap
- floating quest zone that sensor-triggers quest completion
- fog, stars, ambient + accent point light per world

Wires into Playground screen:
- Launch now opens 3D world
- GPU-safe Lite world remains as fallback if WebGL is unavailable
- HUD overlay (XP, inventory, skills, world map) renders on top of 3D

Walking into the portal teleports between Agora and Forge and
auto-unlocks the next world if needed. Walking into the quest zone
completes the active quest and grants reward toast + items.

This establishes the real 3D base. Next push: WebSocket multiplayer
so other players appear in the same world with chat bubbles.

package.json

@@ -34,6 +34,7 @@
     "@monaco-editor/react": "^4.7.0",
     "@react-three/drei": "^10.7.7",
     "@react-three/fiber": "^9.6.1",
+    "@react-three/rapier": "^2.2.0",
     "@tailwindcss/vite": "^4.1.18",
     "@tanstack/react-query": "^5.84.1",
     "@tanstack/react-router": "^1.132.0",
@@ -44,6 +45,7 @@
     "@types/react-grid-layout": "^1.3.6",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
+    "ecctrl": "^1.0.97",
     "electron-updater": "^6.6.2",
     "framer-motion": "^12.36.0",
     "marked": "^17.0.1",