fix(eye-shader): 采样 UV 饱和并统一 half 精度

Co-authored-by: Cursor <cursoragent@cursor.com>

Assets/Render/EyeUnifiedSprite.shader

@@ -133,23 +133,23 @@ Shader "AIBIS/EyeUnifiedSprite"
                 return saturate(mul(mat, color));
             }
 
-            fixed4 sampleMainTex(float2 uv)
+            half4 sampleMainTex(float2 uv)
             {
-                return tex2D(_MainTex, uv);
+                return tex2D(_MainTex, saturate(uv));
             }
 
-            fixed3 GaussianBlurRgb(float2 uv, float stepSize)
+            half3 GaussianBlurRgb(float2 uv, float stepSize)
             {
                 float angle = 1.937315; // ~111 deg, matches MemoryTuningSprite
                 float2 stepDir = float2(sin(angle), cos(angle));
                 float2 stepUv = stepDir * stepSize;
 
 #if defined(SHADER_API_MOBILE)
-                fixed3 rgb = sampleMainTex(uv).rgb * 0.34;
+                half3 rgb = sampleMainTex(uv).rgb * 0.34;
                 rgb += sampleMainTex(uv + stepUv).rgb * 0.33;
                 rgb += sampleMainTex(uv - stepUv).rgb * 0.33;
 #else
-                fixed3 rgb = sampleMainTex(uv).rgb * 0.18;
+                half3 rgb = sampleMainTex(uv).rgb * 0.18;
                 rgb += sampleMainTex(uv + stepUv * 1.0).rgb * 0.15;
                 rgb += sampleMainTex(uv - stepUv * 1.0).rgb * 0.15;
                 rgb += sampleMainTex(uv + stepUv * 2.0).rgb * 0.12;