feat: add Unity 6 client with 2.5D visual system

Unity client features:
- WebSocket connection via NativeWebSocket
- 2.5D agent visuals with programmatic placeholder sprites
- Billboard system for sprites and UI elements
- Floating UI panels (name, HP, energy bars)
- Speech bubble system with pop-in animation
- RTS-style camera controller (WASD + scroll zoom)
- Editor tools for prefab creation and scene setup

Scripts:
- NetworkManager: WebSocket singleton
- GameManager: Agent spawning and event handling
- AgentVisual: 2.5D sprite and UI creation
- Billboard: Camera-facing behavior
- SpeechBubble: Animated dialogue display
- CameraController: RTS camera with UI input detection
- UIManager: HUD and command input

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

unity-client/Assets/TextMesh Pro/Examples & Extras/Scripts/TMP_ExampleScript_01.cs.meta

@@ -0,0 +1,12 @@
+fileFormatVersion: 2
+guid: 6f2c5b59b6874405865e2616e4ec276a
+timeCreated: 1449625634
+licenseType: Pro
+MonoImporter:
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: