fix: format Length values without trailing .0 for whole numbers

Update Length.stringValue to format whole numbers cleanly (100 instead of 100.0)
while preserving precision for fractional values.

This ensures SVG output is clean and human-readable:
- .number(100) → "100"
- .px(100) → "100px"
- .percentage(50) → "50%"
- .em(2.5) → "2.5em"

Update tests to expect clean formatting without .0 suffix.

Author: coenttb

Sources/W3C SVG/W3C_SVG2.Types.Length.swift

@@ -70,26 +70,35 @@ extension W3C_SVG2.Types {
         public var stringValue: String {
             switch self {
             case .number(let value):
-                return "\(value)"
+                return Self.formatValue(value)
             case .percentage(let value):
-                return "\(value)%"
+                return "\(Self.formatValue(value))%"
             case .px(let value):
-                return "\(value)px"
+                return "\(Self.formatValue(value))px"
             case .em(let value):
-                return "\(value)em"
+                return "\(Self.formatValue(value))em"
             case .ex(let value):
-                return "\(value)ex"
+                return "\(Self.formatValue(value))ex"
             case .pt(let value):
-                return "\(value)pt"
+                return "\(Self.formatValue(value))pt"
             case .pc(let value):
-                return "\(value)pc"
+                return "\(Self.formatValue(value))pc"
             case .mm(let value):
-                return "\(value)mm"
+                return "\(Self.formatValue(value))mm"
             case .cm(let value):
-                return "\(value)cm"
+                return "\(Self.formatValue(value))cm"
             case .in(let value):
-                return "\(value)in"
+                return "\(Self.formatValue(value))in"
             }
         }
+
+        /// Format a Double value for SVG, removing unnecessary decimal points
+        private static func formatValue(_ value: Double) -> String {
+            // Simple approach: remove .0 from whole numbers
+            if value.truncatingRemainder(dividingBy: 1) == 0 {
+                return String(Int(value))
+            }
+            return String(value)
+        }
     }
 }

Tests/W3C SVG Tests/W3C_SVG2_Tests.swift

@@ -16,13 +16,13 @@ struct W3C_SVG2_Tests {
         @Test("Length pixels")
         func lengthPixels() {
             let length = W3C_SVG2.Types.Length.px(100)
-            #expect(length.stringValue == "100.0px")
+            #expect(length.stringValue == "100px")
         }
 
         @Test("Length percentage")
         func lengthPercentage() {
             let length = W3C_SVG2.Types.Length.percentage(50)
-            #expect(length.stringValue == "50.0%")
+            #expect(length.stringValue == "50%")
         }
 
         @Test("Length em")