Phase REFACTOR-1: Magic Number → Named Constants (TINY_CLASS_C6/C7)

Replace hardcoded class_idx checks (== 6, == 7) with named macros:
- tiny_class_is_c6(idx) for C6 checks
- tiny_class_is_c7(idx) for C7 checks
- tiny_class_is_ultra(idx) for combined checks

Benefits:
- Self-documenting code (semantic intent is clear)
- Single source of truth for class constants
- Easier to extend to other ULTRA tiers (C5, C8) in future

Changes:
- NEW: core/box/tiny_ultra_classes_box.h (named constants + helpers)
- Modified: core/front/malloc_tiny_fast.h (4 replacements: L181, L193, L326, L337)

No performance impact (zero-cost macros, same compiled code).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

core/box/tiny_ultra_classes_box.h

@@ -0,0 +1,13 @@
+#ifndef HAKMEM_TINY_ULTRA_CLASSES_BOX_H
+#define HAKMEM_TINY_ULTRA_CLASSES_BOX_H
+
+// Purpose: Named constants for ULTRA tier classes (C6, C7)
+#define TINY_CLASS_C6 6
+#define TINY_CLASS_C7 7
+
+// Helper macros for class checking
+#define tiny_class_is_c6(idx)    ((idx) == TINY_CLASS_C6)
+#define tiny_class_is_c7(idx)    ((idx) == TINY_CLASS_C7)
+#define tiny_class_is_ultra(idx) (tiny_class_is_c6(idx) || tiny_class_is_c7(idx))
+
+#endif // HAKMEM_TINY_ULTRA_CLASSES_BOX_H

core/front/malloc_tiny_fast.h

@@ -47,6 +47,7 @@
 // #include "../box/smallobject_core_v6_box.h" // SmallObject Core v6 (C6-only route stub, Phase v6-1)
 #include "../box/tiny_c7_ultra_box.h" // C7 ULTRA stub (UF-1, delegates to v3)
 #include "../box/tiny_c6_ultra_free_box.h" // Phase 4-2: C6 ULTRA-free (free-only, C6-only)
+#include "../box/tiny_ultra_classes_box.h" // Phase REFACTOR-1: Named constants for C6/C7
 #include "../box/tiny_front_v3_env_box.h" // Tiny front v3 snapshot gate
 #include "../box/tiny_heap_env_box.h"   // ENV gate for TinyHeap front (A/B)
 #include "../box/tiny_route_env_box.h"  // Route snapshot (Heap vs Legacy)
@@ -177,7 +178,7 @@ static inline void* malloc_tiny_fast(size_t size) {
     tiny_front_alloc_stat_inc(class_idx);
 
     // C7 ULTRA stub (UF-1): delegates to v3, ENV gated
-    if (class_idx == 7 &&
+    if (tiny_class_is_c7(class_idx) &&
         tiny_front_v3_enabled() &&
         tiny_front_v3_c7_ultra_enabled() &&
         small_heap_v3_c7_enabled()) {
@@ -189,7 +190,7 @@ static inline void* malloc_tiny_fast(size_t size) {
     }
 
     // Phase 4-4: C6 ULTRA free+alloc integration (寄生型 TLS キャッシュ pop)
-    if (class_idx == 6 && tiny_c6_ultra_free_enabled()) {
+    if (tiny_class_is_c6(class_idx) && tiny_c6_ultra_free_enabled()) {
         TinyC6UltraFreeTLS* ctx = tiny_c6_ultra_free_tls();
         if (TINY_HOT_LIKELY(ctx->count > 0)) {
             void* base = ctx->freelist[--ctx->count];
@@ -322,7 +323,7 @@ static inline int free_tiny_fast(void* ptr) {
     FREE_PATH_STAT_INC(total_calls);
 
     // C7 ULTRA stub (UF-1): delegates to v3, ENV gated
-    if (class_idx == 7 &&
+    if (tiny_class_is_c7(class_idx) &&
         tiny_front_v3_enabled() &&
         tiny_front_v3_c7_ultra_enabled() &&
         small_heap_v3_c7_enabled()) {
@@ -333,7 +334,7 @@ static inline int free_tiny_fast(void* ptr) {
     }
 
     // Phase 4-2: C6 ULTRA-free (C6-only, free-only, ENV gated)
-    if (class_idx == 6 && tiny_c6_ultra_free_enabled()) {
+    if (tiny_class_is_c6(class_idx) && tiny_c6_ultra_free_enabled()) {
         tiny_c6_ultra_free_fast(base, class_idx);
         return 1;
     }