feat(prolog): Atom unification

tests/prolog/unifyTest.kt

@@ -0,0 +1,29 @@
+package prolog
+
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.Test
+import prolog.terms.Atom
+
+class unifyTest {
+    @Test
+    fun identical_atoms_unify() {
+        val atom1 = Atom("a")
+        val atom2 = Atom("a")
+
+        val result = unify(atom1, atom2)
+
+        assertTrue(result.success)
+        assertEquals(0, result.substitutions.size)
+    }
+
+    @Test
+    fun different_atoms_do_not_unify() {
+        val atom1 = Atom("a")
+        val atom2 = Atom("b")
+
+        val result = unify(atom1, atom2)
+
+        assertFalse(result.success)
+        assertEquals(0, result.substitutions.size)
+    }
+}