Phase 3d-B: TLS Cache Merge - Unified g_tls_sll[] structure (+12-18% expected)

Merge separate g_tls_sll_head[] and g_tls_sll_count[] arrays into unified
TinyTLSSLL struct to improve L1D cache locality. Expected performance gain:
+12-18% from reducing cache line splits (2 loads → 1 load per operation).

Changes:
- core/hakmem_tiny.h: Add TinyTLSSLL type (16B aligned, head+count+pad)
- core/hakmem_tiny.c: Replace separate arrays with g_tls_sll[8]
- core/box/tls_sll_box.h: Update Box API (13 sites) for unified access
- Updated 32+ files: All g_tls_sll_head[i] → g_tls_sll[i].head
- Updated 32+ files: All g_tls_sll_count[i] → g_tls_sll[i].count
- core/hakmem_tiny_integrity.h: Unified canary guards
- core/box/integrity_box.c: Simplified canary validation
- Makefile: Added core/box/tiny_sizeclass_hist_box.o to link

Build: ✅ PASS (10K ops sanity test)
Warnings: Only pre-existing LTO type mismatches (unrelated)

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

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

core/box/ss_os_acquire_box.h

@@ -0,0 +1,52 @@
+// ss_os_acquire_box.h - SuperSlab OS Memory Acquisition Box
+// Purpose: Low-level OS memory allocation (mmap/munmap) for SuperSlabs
+// Box Theory: Encapsulates platform-specific aligned memory allocation
+//
+// Responsibilities:
+//   - Aligned mmap allocation (2MB boundary)
+//   - OOM diagnostics and error reporting
+//   - Global mmap counters
+//
+// Dependencies: None (pure OS interface)
+//
+// License: MIT
+// Date: 2025-11-19
+
+#ifndef HAKMEM_SS_OS_ACQUIRE_BOX_H
+#define HAKMEM_SS_OS_ACQUIRE_BOX_H
+
+#include <stdint.h>
+#include <stddef.h>
+#include <stdatomic.h>
+
+// ============================================================================
+// Global Counters (for debugging/diagnostics)
+// ============================================================================
+
+extern _Atomic uint64_t g_ss_mmap_count;
+extern _Atomic uint64_t g_final_fallback_mmap_count;
+
+// ============================================================================
+// OS Acquisition API
+// ============================================================================
+
+// Acquire aligned SuperSlab memory from OS via mmap
+//
+// Parameters:
+//   size_class: Size class index (0-7, for statistics)
+//   ss_size: SuperSlab size in bytes (e.g., 2^21 = 2MB)
+//   ss_mask: Alignment mask (ss_size - 1)
+//   populate: If true, use MAP_POPULATE to prefault pages
+//
+// Returns: Aligned pointer or NULL on OOM
+//
+// Guarantees:
+//   - Returns NULL on OOM (never crashes)
+//   - Returned pointer is aligned to ss_size boundary
+//   - Logs OOM once per process (not spammy)
+//   - Updates g_ss_mmap_count counter
+//
+// Thread-safe: Yes (no shared state mutations except atomic counters)
+void* ss_os_acquire(uint8_t size_class, size_t ss_size, uintptr_t ss_mask, int populate);
+
+#endif // HAKMEM_SS_OS_ACQUIRE_BOX_H