Implement Phase 2: Headerless Allocator Support (Partial)

- Feature: Added HAKMEM_TINY_HEADERLESS toggle (A/B testing)
- Feature: Implemented Headerless layout logic (Offset=0)
- Refactor: Centralized layout definitions in tiny_layout_box.h
- Refactor: Abstracted pointer arithmetic in free path via ptr_conversion_box.h
- Verification: sh8bench passes in Headerless mode (No TLS_SLL_HDR_RESET)
- Known Issue: Regression in Phase 1 mode due to blind pointer conversion logic

core/box/hak_core_init.inc.h

@@ -127,7 +127,7 @@ static void hak_init_impl(void) {
 #endif
         HAKMEM_LOG("[Build] Flavor=%s  Flags: HEADER_CLASSIDX=%d, AGGRESSIVE_INLINE=%d, POOL_TLS_PHASE1=%d, POOL_TLS_PREWARM=%d\n",
                    bf,
-#ifdef HAKMEM_TINY_HEADER_CLASSIDX
+#if HAKMEM_TINY_HEADER_CLASSIDX
                    1,
 #else
                    0,