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/DropdownSample.cs

@@ -0,0 +1,19 @@
+using TMPro;
+using UnityEngine;
+
+public class DropdownSample: MonoBehaviour
+{
+	[SerializeField]
+	private TextMeshProUGUI text = null;
+
+	[SerializeField]
+	private TMP_Dropdown dropdownWithoutPlaceholder = null;
+
+	[SerializeField]
+	private TMP_Dropdown dropdownWithPlaceholder = null;
+
+	public void OnButtonClick()
+	{
+		text.text = dropdownWithPlaceholder.value > -1 ? "Selected values:\n" + dropdownWithoutPlaceholder.value + " - " + dropdownWithPlaceholder.value : "Error: Please make a selection";
+	}
+}