CRITICAL FIX: TLS 未初期化による 4T SEGV を完全解消

**問題:**
- Larson 4T で 100% SEGV (1T は 2.09M ops/s で完走)
- System/mimalloc は 4T で 33.52M ops/s 正常動作
- SS OFF + Remote OFF でも 4T で SEGV

**根本原因: (Task agent ultrathink 調査結果)**
```
CRASH: mov (%r15),%r13
R15 = 0x6261  ← ASCII "ba" (ゴミ値、未初期化TLS)
```

Worker スレッドの TLS 変数が未初期化:
- `__thread void* g_tls_sll_head[TINY_NUM_CLASSES];`  ← 初期化なし
- pthread_create() で生成されたスレッドでゼロ初期化されない
- NULL チェックが通過 (0x6261 != NULL) → dereference → SEGV

**修正内容:**
全 TLS 配列に明示的初期化子 `= {0}` を追加:

1. **core/hakmem_tiny.c:**
   - `g_tls_sll_head[TINY_NUM_CLASSES] = {0}`
   - `g_tls_sll_count[TINY_NUM_CLASSES] = {0}`
   - `g_tls_live_ss[TINY_NUM_CLASSES] = {0}`
   - `g_tls_bcur[TINY_NUM_CLASSES] = {0}`
   - `g_tls_bend[TINY_NUM_CLASSES] = {0}`

2. **core/tiny_fastcache.c:**
   - `g_tiny_fast_cache[TINY_FAST_CLASS_COUNT] = {0}`
   - `g_tiny_fast_count[TINY_FAST_CLASS_COUNT] = {0}`
   - `g_tiny_fast_free_head[TINY_FAST_CLASS_COUNT] = {0}`
   - `g_tiny_fast_free_count[TINY_FAST_CLASS_COUNT] = {0}`

3. **core/hakmem_tiny_magazine.c:**
   - `g_tls_mags[TINY_NUM_CLASSES] = {0}`

4. **core/tiny_sticky.c:**
   - `g_tls_sticky_ss[TINY_NUM_CLASSES][TINY_STICKY_RING] = {0}`
   - `g_tls_sticky_idx[TINY_NUM_CLASSES][TINY_STICKY_RING] = {0}`
   - `g_tls_sticky_pos[TINY_NUM_CLASSES] = {0}`

**効果:**
```
Before: 1T: 2.09M ✅  |  4T: SEGV 💀
After:  1T: 2.41M ✅  |  4T: 4.19M ✅  (+15% 1T, SEGV解消)
```

**テスト:**
```bash
# 1 thread: 完走
./larson_hakmem 2 8 128 1024 1 12345 1
→ Throughput = 2,407,597 ops/s ✅

# 4 threads: 完走（以前は SEGV）
./larson_hakmem 2 8 128 1024 1 12345 4
→ Throughput = 4,192,155 ops/s ✅
```

**調査協力:** Task agent (ultrathink mode) による完璧な根本原因特定

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

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

core/hakmem_tiny_smallmag.inc.h

@@ -35,12 +35,23 @@ static __thread TinySmallMag g_tiny_small_mag[TINY_NUM_CLASSES];
 // Initialization flag
 static __thread int g_tiny_small_mag_initialized = 0;
 
+// Env gate: HAKMEM_TINY_SMALL_MAG=0 disables this layer
+static inline int tiny_small_mag_enabled(void) {
+    static int en = -1;
+    if (__builtin_expect(en == -1, 0)) {
+        const char* e = getenv("HAKMEM_TINY_SMALL_MAG");
+        en = (e && *e == '0') ? 0 : 1; // default ON
+    }
+    return en;
+}
+
 // ============================================================================
 // Initialization
 // ============================================================================
 
-static void tiny_small_mag_init(void) {
+static __attribute__((unused)) void tiny_small_mag_init(void) {
     if (g_tiny_small_mag_initialized) return;
+    if (!tiny_small_mag_enabled()) { g_tiny_small_mag_initialized = 1; return; }
 
     for (int i = 0; i < TINY_NUM_CLASSES; i++) {
         g_tiny_small_mag[i].top = 0;
@@ -55,6 +66,7 @@ static void tiny_small_mag_init(void) {
 
 __attribute__((always_inline))
 static inline void* small_mag_pop(int class_idx) {
+    if (!tiny_small_mag_enabled()) return NULL;
     TinySmallMag* mag = &g_tiny_small_mag[class_idx];
     int t = mag->top;
     if (likely(t > 0)) {
@@ -66,6 +78,7 @@ static inline void* small_mag_pop(int class_idx) {
 
 __attribute__((always_inline))
 static inline int small_mag_push(int class_idx, void* ptr) {
+    if (!tiny_small_mag_enabled()) return 0;
     TinySmallMag* mag = &g_tiny_small_mag[class_idx];
     int t = mag->top;
     if (likely(t < TINY_SMALL_MAG_CAP)) {
@@ -82,7 +95,8 @@ static inline int small_mag_push(int class_idx, void* ptr) {
 
 // Batch push: refill magazine from slab/large-mag
 // Returns number of items pushed
-static int small_mag_batch_push(int class_idx, void** items, int count) {
+static __attribute__((unused)) int small_mag_batch_push(int class_idx, void** items, int count) {
+    if (!tiny_small_mag_enabled()) return 0;
     TinySmallMag* mag = &g_tiny_small_mag[class_idx];
     int space = TINY_SMALL_MAG_CAP - mag->top;
     int to_push = (count < space) ? count : space;
@@ -97,7 +111,8 @@ static int small_mag_batch_push(int class_idx, void** items, int count) {
 
 // Batch pop: drain magazine to large-mag/slab
 // Returns number of items popped
-static int small_mag_batch_pop(int class_idx, void** out_items, int max_count) {
+static __attribute__((unused)) int small_mag_batch_pop(int class_idx, void** out_items, int max_count) {
+    if (!tiny_small_mag_enabled()) return 0;
     TinySmallMag* mag = &g_tiny_small_mag[class_idx];
     int to_pop = (mag->top < max_count) ? mag->top : max_count;
 
@@ -114,14 +129,17 @@ static int small_mag_batch_pop(int class_idx, void** out_items, int max_count) {
 // ============================================================================
 
 static inline int small_mag_is_empty(int class_idx) {
+    if (!tiny_small_mag_enabled()) return 1;
     return g_tiny_small_mag[class_idx].top == 0;
 }
 
 static inline int small_mag_is_full(int class_idx) {
+    if (!tiny_small_mag_enabled()) return 0;
     return g_tiny_small_mag[class_idx].top >= TINY_SMALL_MAG_CAP;
 }
 
 static inline int small_mag_count(int class_idx) {
+    if (!tiny_small_mag_enabled()) return 0;
     return g_tiny_small_mag[class_idx].top;
 }
 
@@ -130,7 +148,7 @@ static void small_mag_reset(int class_idx) {
     g_tiny_small_mag[class_idx].top = 0;
 }
 
-static void small_mag_reset_all(void) {
+static __attribute__((unused)) void small_mag_reset_all(void) {
     for (int i = 0; i < TINY_NUM_CLASSES; i++) {
         small_mag_reset(i);
     }