Priority-2 ENV Cache: hakmem_smallmid.c (1変数追加、1箇所置換)

【追加ENV変数】
- HAKMEM_SMALLMID_ENABLE (default: 0)

【置換ファイル】
- core/hakmem_smallmid.c (1箇所 → ENV Cache)

【変更詳細】
1. ENV Cache (hakmem_env_cache.h):
   - 構造体に1変数追加 (46→47変数)
   - hakmem_env_cache_init()に初期化追加
   - アクセサマクロ追加
   - カウント更新: 46→47

2. hakmem_smallmid.c:
   - smallmid_is_enabled():
     getenv("HAKMEM_SMALLMID_ENABLE") → HAK_ENV_SMALLMID_ENABLE()
   - #include "hakmem_env_cache.h" 追加

【効果】
- SmallMid有効化チェックからgetenv()呼び出しを排除
- Warm path起動時のENV参照を1回に削減

【テスト】
✅ make shared → 成功
✅ /tmp/test_mixed3_final → PASSED

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

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

core/hakmem_env_cache.h

@@ -81,6 +81,9 @@ typedef struct {
     int tiny_tension_drain_enable;   // HAKMEM_TINY_TENSION_DRAIN_ENABLE (default: 1)
     int tiny_tension_drain_threshold; // HAKMEM_TINY_TENSION_DRAIN_THRESHOLD (default: 1024)
 
+    // ===== Warm Path: SmallMid (1 variable) =====
+    int smallmid_enable;             // HAKMEM_SMALLMID_ENABLE (default: 0)
+
 } HakEnvCache;
 
 // Global cache instance (initialized once at startup)
@@ -258,10 +261,17 @@ static inline void hakmem_env_cache_init(void) {
         if (g_hak_env_cache.tiny_tension_drain_threshold > 65536) g_hak_env_cache.tiny_tension_drain_threshold = 65536;
     }
 
+    // ===== Warm Path: SmallMid =====
+    {
+        const char* e;
+        e = getenv("HAKMEM_SMALLMID_ENABLE");
+        g_hak_env_cache.smallmid_enable = (e && atoi(e) == 1) ? 1 : 0;  // default: 0 (OFF)
+    }
+
 #if !HAKMEM_BUILD_RELEASE
     // Debug: Print cache summary (stderr only)
     if (!g_hak_env_cache.quiet) {
-        fprintf(stderr, "[ENV_CACHE_INIT] Parsed %d ENV variables at startup\n", 46);
+        fprintf(stderr, "[ENV_CACHE_INIT] Parsed %d ENV variables at startup\n", 47);
         fprintf(stderr, "[ENV_CACHE_INIT] Hot path syscalls eliminated: ~2000/sec → 0/sec\n");
         fflush(stderr);
     }
@@ -321,4 +331,7 @@ static inline void hakmem_env_cache_init(void) {
 #define HAK_ENV_TINY_TENSION_DRAIN_ENABLE() (g_hak_env_cache.tiny_tension_drain_enable)
 #define HAK_ENV_TINY_TENSION_DRAIN_THRESHOLD() (g_hak_env_cache.tiny_tension_drain_threshold)
 
+// Warm path: SmallMid
+#define HAK_ENV_SMALLMID_ENABLE()           (g_hak_env_cache.smallmid_enable)
+
 #endif // HAKMEM_ENV_CACHE_H