test: add ResizeHandle enum unit tests

Add 10 tests covering the ResizeHandle enum:
- Verify all 8 handles exist
- Verify each handle name (NW, N, NE, E, SE, S, SW, W)
- Verify each handle maps to the correct java.awt.Cursor constant
- Verify valueOf() round-trip for all handles
- Verify valueOf() with invalid name throws IllegalArgumentException

Closes #12

src/test/java/ovh/gasser/newshapes/shapes/ResizeHandleTest.java

@@ -0,0 +1,94 @@
+package ovh.gasser.newshapes.shapes;
+
+import org.junit.jupiter.api.Test;
+import java.awt.Cursor;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class ResizeHandleTest {
+
+    @Test
+    void testEightHandlesExist() {
+        assertEquals(8, ResizeHandle.values().length,
+                "ResizeHandle enum should define exactly 8 handles");
+    }
+
+    @Test
+    void testAllHandleNamesExist() {
+        assertNotNull(ResizeHandle.valueOf("NW"), "Handle NW should exist");
+        assertNotNull(ResizeHandle.valueOf("N"),  "Handle N should exist");
+        assertNotNull(ResizeHandle.valueOf("NE"), "Handle NE should exist");
+        assertNotNull(ResizeHandle.valueOf("E"),  "Handle E should exist");
+        assertNotNull(ResizeHandle.valueOf("SE"), "Handle SE should exist");
+        assertNotNull(ResizeHandle.valueOf("S"),  "Handle S should exist");
+        assertNotNull(ResizeHandle.valueOf("SW"), "Handle SW should exist");
+        assertNotNull(ResizeHandle.valueOf("W"),  "Handle W should exist");
+    }
+
+    @Test
+    void testNwMapsToCorrectCursorType() {
+        assertEquals(Cursor.NW_RESIZE_CURSOR, ResizeHandle.NW.getCursorType(),
+                "NW handle should map to Cursor.NW_RESIZE_CURSOR");
+    }
+
+    @Test
+    void testNMapsToCorrectCursorType() {
+        assertEquals(Cursor.N_RESIZE_CURSOR, ResizeHandle.N.getCursorType(),
+                "N handle should map to Cursor.N_RESIZE_CURSOR");
+    }
+
+    @Test
+    void testNeMapsToCorrectCursorType() {
+        assertEquals(Cursor.NE_RESIZE_CURSOR, ResizeHandle.NE.getCursorType(),
+                "NE handle should map to Cursor.NE_RESIZE_CURSOR");
+    }
+
+    @Test
+    void testEMapsToCorrectCursorType() {
+        assertEquals(Cursor.E_RESIZE_CURSOR, ResizeHandle.E.getCursorType(),
+                "E handle should map to Cursor.E_RESIZE_CURSOR");
+    }
+
+    @Test
+    void testSeMapsToCorrectCursorType() {
+        assertEquals(Cursor.SE_RESIZE_CURSOR, ResizeHandle.SE.getCursorType(),
+                "SE handle should map to Cursor.SE_RESIZE_CURSOR");
+    }
+
+    @Test
+    void testSMapsToCorrectCursorType() {
+        assertEquals(Cursor.S_RESIZE_CURSOR, ResizeHandle.S.getCursorType(),
+                "S handle should map to Cursor.S_RESIZE_CURSOR");
+    }
+
+    @Test
+    void testSwMapsToCorrectCursorType() {
+        assertEquals(Cursor.SW_RESIZE_CURSOR, ResizeHandle.SW.getCursorType(),
+                "SW handle should map to Cursor.SW_RESIZE_CURSOR");
+    }
+
+    @Test
+    void testWMapsToCorrectCursorType() {
+        assertEquals(Cursor.W_RESIZE_CURSOR, ResizeHandle.W.getCursorType(),
+                "W handle should map to Cursor.W_RESIZE_CURSOR");
+    }
+
+    @Test
+    void testValueOfReturnsCorrectConstant() {
+        assertSame(ResizeHandle.NW, ResizeHandle.valueOf("NW"), "valueOf(\"NW\") should return ResizeHandle.NW");
+        assertSame(ResizeHandle.N,  ResizeHandle.valueOf("N"),  "valueOf(\"N\") should return ResizeHandle.N");
+        assertSame(ResizeHandle.NE, ResizeHandle.valueOf("NE"), "valueOf(\"NE\") should return ResizeHandle.NE");
+        assertSame(ResizeHandle.E,  ResizeHandle.valueOf("E"),  "valueOf(\"E\") should return ResizeHandle.E");
+        assertSame(ResizeHandle.SE, ResizeHandle.valueOf("SE"), "valueOf(\"SE\") should return ResizeHandle.SE");
+        assertSame(ResizeHandle.S,  ResizeHandle.valueOf("S"),  "valueOf(\"S\") should return ResizeHandle.S");
+        assertSame(ResizeHandle.SW, ResizeHandle.valueOf("SW"), "valueOf(\"SW\") should return ResizeHandle.SW");
+        assertSame(ResizeHandle.W,  ResizeHandle.valueOf("W"),  "valueOf(\"W\") should return ResizeHandle.W");
+    }
+
+    @Test
+    void testValueOfWithInvalidNameThrowsIllegalArgumentException() {
+        assertThrows(IllegalArgumentException.class,
+                () -> ResizeHandle.valueOf("INVALID"),
+                "valueOf() with an unknown name should throw IllegalArgumentException");
+    }
+}