Fix swapped LeftNode and RightNode in exclusiveMaximum PropertyCheck

Fixes issue where LeftNode was assigned rnv and RightNode was assigned lnv,
causing incorrect node references in change detection for exclusiveMaximum
property comparisons.

Addresses #451

Author: califlower

what-changed/model/schema.go

@@ -761,8 +761,8 @@ func checkSchemaPropertyChanges(
 	}
 	// ExclusiveMaximum
 	props = append(props, &PropertyCheck{
-		LeftNode:  rnv,
-		RightNode: lnv,
+		LeftNode:  lnv,
+		RightNode: rnv,
 		Label:     v3.ExclusiveMaximumLabel,
 		Changes:   changes,
 		Breaking:  true,

what-changed/model/schema_test.go

@@ -3591,6 +3591,45 @@ components:
 	changes.PropertiesOnly() // this does nothing in this lib.
 }
 
+func TestCompareSchemas_ExclusiveMaximumNodeSwap(t *testing.T) {
+	// Clear hash cache to ensure deterministic results in concurrent test environments
+	low.ClearHashCache()
+	left := `openapi: 3.1
+components:
+  schemas:
+    TestSchema:
+      type: number
+      exclusiveMaximum: 100`
+
+	right := `openapi: 3.1
+components:
+  schemas:
+    TestSchema:
+      type: number
+      exclusiveMaximum: 200`
+
+	leftDoc, rightDoc := test_BuildDoc(left, right)
+
+	// extract left reference schema and non reference schema.
+	lSchemaProxy := leftDoc.Components.Value.FindSchema("TestSchema").Value
+	rSchemaProxy := rightDoc.Components.Value.FindSchema("TestSchema").Value
+
+	changes := CompareSchemas(lSchemaProxy, rSchemaProxy)
+	assert.NotNil(t, changes)
+	assert.Len(t, changes.GetAllChanges(), 1)
+	assert.Equal(t, changes.TotalChanges(), 1)
+	assert.Equal(t, changes.TotalBreakingChanges(), 1)
+
+	// Find the exclusiveMaximum change
+	exclusiveMaxChange := changes.GetPropertyChanges()[0]
+	assert.Equal(t, "exclusiveMaximum", exclusiveMaxChange.Property)
+	assert.Equal(t, Modified, exclusiveMaxChange.ChangeType)
+
+	// Test the values are correct
+	assert.Equal(t, "100", exclusiveMaxChange.Original)
+	assert.Equal(t, "200", exclusiveMaxChange.New)
+}
+
 func TestCompareSchemas_CheckXML(t *testing.T) {
 	// Clear hash cache to ensure deterministic results in concurrent test environments
 	low.ClearHashCache()