[GFX-724] fix(runtime): PathHelper.Combine 绝对路径段正确追加分隔符

Runtime/Helper/PathHelper.cs

@@ -115,11 +115,6 @@ public static string Combine(params string[] paths)
                     continue;
                 }
 
-                if (path.StartsWithFast(separatorA) || path.StartsWithFast(separatorB))
-                {
-                    continue;
-                }
-
                 sb.Append(separatorA);
             }
 

Tests/UtilityPathTests.cs

@@ -225,5 +225,58 @@ public void RemoveEmptyDirectory_DirWithNonEmptySubDir_ReturnsFalse()
         }
 
         #endregion
+
+        #region PathHelper.Combine
+
+        [Test]
+        public void Combine_SingleSegment_ReturnsUnchanged()
+        {
+            string result = PathHelper.Combine("img.png");
+            Assert.AreEqual("img.png", result);
+        }
+
+        [Test]
+        public void Combine_TwoRelativeSegments_AddsSeparator()
+        {
+            string result = PathHelper.Combine("cache", "img.png");
+            Assert.AreEqual("cache/img.png", result);
+        }
+
+        [Test]
+        public void Combine_AbsolutePathSegment_AppendsSeparator()
+        {
+            string result = PathHelper.Combine("/Users/blank/cache", "img.png");
+            Assert.AreEqual("/Users/blank/cache/img.png", result);
+        }
+
+        [Test]
+        public void Combine_TrailingSlashSegment_DoesNotDuplicate()
+        {
+            string result = PathHelper.Combine("cache/", "img.png");
+            Assert.AreEqual("cache/img.png", result);
+        }
+
+        [Test]
+        public void Combine_PureSeparatorSegment_DoesNotDuplicate()
+        {
+            string result = PathHelper.Combine("/", "img.png");
+            Assert.AreEqual("/img.png", result);
+        }
+
+        [Test]
+        public void Combine_TrailingBackslashSegment_DoesNotDuplicate()
+        {
+            string result = PathHelper.Combine("dir\\", "file.txt");
+            Assert.AreEqual("dir\\file.txt", result);
+        }
+
+        [Test]
+        public void Combine_MultipleSegments_AbsolutePathJoint()
+        {
+            string result = PathHelper.Combine("/Users", "blank", "cache", "img.png");
+            Assert.AreEqual("/Users/blank/cache/img.png", result);
+        }
+
+        #endregion
     }
 }