feat: Phase 19-C/D - sprite loading, transparency, and animation

- Add runtime sprite loading from Characters.png and Environment.png
- Implement ProcessTransparency for chroma-key white background removal
- Add AgentAnimator for procedural idle/movement animations
- Add Billboard component support for 2.5D perspective
- Normalize sprite scales based on world units
- Fix SetMovement parameter mismatch

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

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

unity-client/Assets/Scripts/Visual/AgentAnimator.cs

@@ -0,0 +1,123 @@
+using UnityEngine;
+using System.Collections;
+
+namespace TheIsland
+{
+    /// <summary>
+    /// Procedural 2D animator for agents. 
+    /// Handles idle breathing, movement bopping, and action-based squash/stretch.
+    /// </summary>
+    public class AgentAnimator : MonoBehaviour
+    {
+        [Header("Animation Settings")]
+        public float idleSpeed = 2f;
+        public float idleAmount = 0.05f;
+        public float moveBopSpeed = 12f;
+        public float moveBopAmount = 0.12f;
+        public float moveTiltAmount = 8f;
+        
+        private SpriteRenderer _spriteRenderer;
+        private Vector3 _originalScale;
+        private Vector3 _targetLocalPos;
+        private Quaternion _targetLocalRot;
+        private Vector3 _targetScale;
+        
+        private float _velocityPercentage; // 0 to 1
+        private bool _isMoving;
+
+        private void Awake()
+        {
+            // Find in children if not on this object
+            _spriteRenderer = GetComponentInChildren<SpriteRenderer>();
+        }
+
+        private void Start()
+        {
+            if (_spriteRenderer != null)
+            {
+                _originalScale = _spriteRenderer.transform.localScale;
+            }
+            else
+            {
+                _originalScale = Vector3.one;
+            }
+        }
+
+        public void SetMovement(float currentVelocity, float maxVelocity)
+        {
+            _velocityPercentage = Mathf.Clamp01(currentVelocity / Mathf.Max(0.1f, maxVelocity));
+            _isMoving = _velocityPercentage > 0.05f;
+        }
+
+        public void TriggerActionEffect()
+        {
+            StopAllCoroutines();
+            StartCoroutine(ActionPulseRoutine());
+        }
+
+        private void Update()
+        {
+            if (_spriteRenderer == null) return;
+
+            if (_isMoving)
+            {
+                AnimateMove();
+            }
+            else
+            {
+                AnimateIdle();
+            }
+
+            // Smoothly apply transforms
+            _spriteRenderer.transform.localPosition = Vector3.Lerp(_spriteRenderer.transform.localPosition, _targetLocalPos, Time.deltaTime * 10f);
+            _spriteRenderer.transform.localRotation = Quaternion.Slerp(_spriteRenderer.transform.localRotation, _targetLocalRot, Time.deltaTime * 10f);
+            _spriteRenderer.transform.localScale = Vector3.Lerp(_spriteRenderer.transform.localScale, _targetScale, Time.deltaTime * 10f);
+        }
+
+        private void AnimateIdle()
+        {
+            // Idle "Breathing"
+            float breathe = Mathf.Sin(Time.time * idleSpeed) * idleAmount;
+            
+            _targetScale = new Vector3(_originalScale.x, _originalScale.y * (1f + breathe), _originalScale.z);
+            _targetLocalPos = Vector3.zero;
+            _targetLocalRot = Quaternion.identity;
+        }
+
+        private void AnimateMove()
+        {
+            // Movement "Bopping" - Sin wave for vertical bounce
+            float cycle = Time.time * moveBopSpeed;
+            float bop = Mathf.Abs(Mathf.Sin(cycle)) * moveBopAmount * _velocityPercentage;
+            
+            // Tilt based on the cycle to give a "walking" feel
+            float tilt = Mathf.Sin(cycle) * moveTiltAmount * _velocityPercentage;
+            
+            _targetLocalPos = new Vector3(0, bop, 0);
+            _targetLocalRot = Quaternion.Euler(0, 0, tilt);
+            
+            // Squash and stretch during the bop
+            float stretch = 1f + bop;
+            float squash = 1f / stretch;
+            _targetScale = new Vector3(_originalScale.x * stretch, _originalScale.y * squash, _originalScale.z);
+        }
+
+        private IEnumerator ActionPulseRoutine()
+        {
+            float elapsed = 0;
+            float duration = 0.25f;
+            while (elapsed < duration)
+            {
+                elapsed += Time.deltaTime;
+                float t = elapsed / duration;
+                // Double pulse or overshoot
+                float scale = 1.0f + Mathf.Sin(t * Mathf.PI) * 0.4f;
+                
+                // Override target scale briefly
+                _spriteRenderer.transform.localScale = new Vector3(_originalScale.x * scale, _originalScale.y * (2f - scale), _originalScale.z);
+                yield return null;
+            }
+            _targetScale = _originalScale;
+        }
+    }
+}

unity-client/Assets/Scripts/Visual/AgentAnimator.cs.meta

@@ -0,0 +1,2 @@
+fileFormatVersion: 2
+guid: 4b9e1cbf8a16c41ccb4b5f197e3ade72

unity-client/Assets/Scripts/Visual/EnvironmentManager.cs

@@ -437,8 +437,17 @@ namespace TheIsland.Visual
             var trunkRenderer = trunkSprite.AddComponent<SpriteRenderer>();
             trunkRenderer.sprite = CreateTreeSprite();
             trunkRenderer.sortingOrder = -20;
-            // Phase 19-B: Uniform scale to avoid distortion
-            trunkSprite.transform.localScale = new Vector3(scale, scale, 1);
+            
+            // Phase 19-C: Add Billboard for 2.5D perspective
+            trunkSprite.AddComponent<Billboard>();
+            
+            // Phase 19-C: Normalize scale based on world units. 
+            // If the sprite is large, we want it to fit the intended 'scale' height.
+            // A typical tree sprite at 100 PPU might be 10 units high. 
+            // We want it to be 'scale' units high (e.g. 3 units).
+            float spriteHeightUnits = trunkRenderer.sprite.rect.height / trunkRenderer.sprite.pixelsPerUnit;
+            float normScale = scale / spriteHeightUnits;
+            trunkSprite.transform.localScale = new Vector3(normScale, normScale, 1);
         }
 
         private Texture2D _envTexture;
@@ -449,33 +458,39 @@ namespace TheIsland.Visual
             if (System.IO.File.Exists(path))
             {
                 byte[] data = System.IO.File.ReadAllBytes(path);
-                _envTexture = new Texture2D(2, 2);
-                _envTexture.LoadImage(data);
+                Texture2D sourceTex = new Texture2D(2, 2);
+                sourceTex.LoadImage(data);
                 
-                // Phase 19-B: Fix white background transparency
-                ProcessTransparency(_envTexture);
+                // Phase 19-C: Robust transparency transcoding
+                _envTexture = ProcessTransparency(sourceTex);
             }
         }
 
-        private void ProcessTransparency(Texture2D tex)
+        private Texture2D ProcessTransparency(Texture2D source)
         {
-            if (tex == null) return;
-            Color[] pixels = tex.GetPixels();
-            bool changed = false;
+            if (source == null) return null;
+            
+            // Create a new texture with Alpha channel
+            Texture2D tex = new Texture2D(source.width, source.height, TextureFormat.RGBA32, false);
+            Color[] pixels = source.GetPixels();
+            
             for (int i = 0; i < pixels.Length; i++)
             {
-                // If the pixel is very close to white, make it transparent
-                if (pixels[i].r > 0.92f && pixels[i].g > 0.92f && pixels[i].b > 0.92f)
+                Color p = pixels[i];
+                // Chroma-key: If pixel is very close to white, make it transparent
+                if (p.r > 0.9f && p.g > 0.9f && p.b > 0.9f)
                 {
-                    pixels[i] = Color.clear;
-                    changed = true;
+                    pixels[i] = new Color(0, 0, 0, 0);
+                }
+                else
+                {
+                    pixels[i] = new Color(p.r, p.g, p.b, 1.0f);
                 }
             }
-            if (changed)
-            {
-                tex.SetPixels(pixels);
-                tex.Apply();
-            }
+            
+            tex.SetPixels(pixels);
+            tex.Apply();
+            return tex;
         }
 
         private Sprite CreateTreeSprite()
@@ -606,7 +621,14 @@ namespace TheIsland.Visual
             var rockRenderer = rockObj.AddComponent<SpriteRenderer>();
             rockRenderer.sprite = CreateRockSprite();
             rockRenderer.sortingOrder = -15;
-            rockObj.transform.localScale = Vector3.one * scale;
+            
+            // Phase 19-C: Add Billboard
+            rockObj.AddComponent<Billboard>();
+            
+            // Phase 19-C: Normalize scale
+            float spriteWidthUnits = rockRenderer.sprite.rect.width / rockRenderer.sprite.pixelsPerUnit;
+            float normScale = scale / spriteWidthUnits;
+            rockObj.transform.localScale = Vector3.one * normScale;
         }
 
         private Sprite CreateRockSprite()