feat: 双Pass膨胀描边shader替代LineRenderer

- 新增 Custom/OutlineUnlit shader: Pass1膨胀描边(Cull Front)+Pass2内芯填充
- BlueOutline.mat: 蓝色描边+半透蓝填充
- TouchPositionHandler改用MeshRenderer.enabled闪烁
- 球体挂MeshRenderer+Outline材质，0.4s闪烁

Assets/Shaders/OutlineUnlit.shader

@@ -0,0 +1,64 @@
+Shader "Custom/OutlineUnlit"
+{
+    Properties
+    {
+        _MainColor ("Main Color", Color) = (0.1, 0.3, 0.8, 0.3)
+        _OutlineColor ("Outline Color", Color) = (0.2, 0.5, 1, 1)
+        _OutlineWidth ("Outline Width", Range(0, 0.3)) = 0.08
+    }
+    SubShader
+    {
+        Tags { "RenderType"="Transparent" "Queue"="Transparent" }
+        Blend SrcAlpha OneMinusSrcAlpha
+        ZWrite Off
+
+        // Pass 1: 膨胀描边
+        Pass
+        {
+            Name "OUTLINE"
+            Cull Front
+            CGPROGRAM
+            #pragma vertex vert
+            #pragma fragment frag
+            #include "UnityCG.cginc"
+
+            float _OutlineWidth;
+            float4 _OutlineColor;
+
+            struct appdata { float4 vertex : POSITION; float3 normal : NORMAL; };
+            struct v2f { float4 pos : SV_POSITION; };
+
+            v2f vert(appdata v)
+            {
+                v2f o;
+                float3 n = normalize(v.normal);
+                v.vertex.xyz += n * _OutlineWidth;
+                o.pos = UnityObjectToClipPos(v.vertex);
+                return o;
+            }
+
+            fixed4 frag(v2f i) : SV_Target { return _OutlineColor; }
+            ENDCG
+        }
+
+        // Pass 2: 内芯填充
+        Pass
+        {
+            Name "FILL"
+            Cull Back
+            CGPROGRAM
+            #pragma vertex vert
+            #pragma fragment frag
+            #include "UnityCG.cginc"
+
+            float4 _MainColor;
+
+            struct appdata { float4 vertex : POSITION; };
+            struct v2f { float4 pos : SV_POSITION; };
+
+            v2f vert(appdata v) { v2f o; o.pos = UnityObjectToClipPos(v.vertex); return o; }
+            fixed4 frag(v2f i) : SV_Target { return _MainColor; }
+            ENDCG
+        }
+    }
+}

Assets/Shaders/OutlineUnlit.shader.meta

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