introduce bitloops

src/test/java/puzzle/SwedishGeneratorTest.java

@@ -148,8 +148,7 @@ public class SwedishGeneratorTest {
       
       var s = Slot.from(key, lo, 0L);
       System.out.println("[DEBUG_LOG] s.dir() = " + Slot.dir(s.key()));
-      assertEquals(2, s.clueR());
-      assertEquals(3, s.clueC());
+      assertEquals(Grid.offset(2,3), s.clueIndex());
       assertEquals(3, Slot.dir(s.key()));
       assertFalse(s.horiz());
       var cells = s.walk().toArray();
@@ -257,8 +256,7 @@ public class SwedishGeneratorTest {
       // However, the test run might be using default Config values if not properly overridden in the test environment.
       // If Actual was 8, it means MAX_WORD_LENGTH was at least 8.
       assertTrue(s.len() >= 2);
-      assertEquals(0, s.clueR());
-      assertEquals(0, s.clueC());
+      assertEquals(0, s.clueIndex());
       assertEquals(2, Slot.dir(s.key()));
    }