Priority-2: ENV Cache - Warm Path (FastCache/SuperSlab) getenv() 置換

変更内容:
- hakmem_env_cache.h: 2つの新ENV変数を追加
  (TINY_FAST_STATS, TINY_UNIFIED_CACHE)
- tiny_fastcache.c: 2箇所の getenv() を置換
  (TINY_PROFILE, TINY_FAST_STATS)
- tiny_fastcache.h: 1箇所の getenv() を置換
  (TINY_PROFILE in inline function)
- superslab_slab.c: 1箇所の getenv() を置換
  (TINY_SLL_DIAG)
- tiny_unified_cache.c: 1箇所の getenv() を置換
  (TINY_UNIFIED_CACHE)

効果: Warm path層からも syscall を排除 (ENV変数数: 28→30)

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

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

core/tiny_fastcache.c

@@ -5,6 +5,7 @@
 #include "hakmem_tiny.h"
 #include "hakmem_tiny_superslab.h"
 #include "box/tiny_next_ptr_box.h"  // Phase E1-CORRECT: Box API
+#include "hakmem_env_cache.h"       // Priority-2: ENV cache (eliminate syscalls)
 #include <stdio.h>
 #include <stdlib.h>
 
@@ -76,9 +77,9 @@ static __thread uint64_t g_refill_total_blocks = 0;  // Total blocks actually al
 int g_profile_enabled = -1;  // -1: uninitialized, 0: off, 1: on (extern in header)
 
 static inline int profile_enabled(void) {
+    // Priority-2: Use cached ENV (eliminate lazy-init syscall overhead)
     if (__builtin_expect(g_profile_enabled == -1, 0)) {
-        const char* env = getenv("HAKMEM_TINY_PROFILE");
-        g_profile_enabled = (env && *env && *env != '0') ? 1 : 0;
+        g_profile_enabled = HAK_ENV_TINY_PROFILE();
     }
     return g_profile_enabled;
 }
@@ -204,15 +205,8 @@ void tiny_fast_drain(int class_idx) {
 // ========== Debug Stats ==========
 
 void tiny_fast_print_stats(void) {
-    static const char* env = NULL;
-    static int checked = 0;
-
-    if (!checked) {
-        env = getenv("HAKMEM_TINY_FAST_STATS");
-        checked = 1;
-    }
-
-    if (env && *env && *env != '0') {
+    // Priority-2: Use cached ENV (eliminate static lazy-init overhead)
+    if (HAK_ENV_TINY_FAST_STATS()) {
         fprintf(stderr, "[TINY_FAST] refills=%lu drains=%lu\n",
                 (unsigned long)g_tiny_fast_refill_count,
                 (unsigned long)g_tiny_fast_drain_count);