Phase 36-37: TinyHotHeap v2 HotBox redesign and C7 current_page policy fixes

- Redefine TinyHotHeap v2 as per-thread Hot Box with clear boundaries
- Add comprehensive OS statistics tracking for SS allocations
- Implement route-based free handling for TinyHeap v2
- Add C6/C7 debugging and statistics improvements
- Update documentation with implementation guidelines and analysis
- Add new box headers for stats, routing, and front-end management

core/box/ss_allocation_box.c

@@ -361,6 +361,7 @@ void superslab_free(SuperSlab* ss) {
         if (lazy_zero_enabled) {
 #ifdef MADV_DONTNEED
             (void)madvise((void*)ss, ss_size, MADV_DONTNEED);
+            ss_os_stats_record_madvise();
 #endif
         }
         return;
@@ -399,6 +400,7 @@ void superslab_free(SuperSlab* ss) {
             atomic_load_explicit(&ss->total_active_blocks, memory_order_relaxed));
 #endif
 
+    ss_os_stats_record_free();
     munmap(ss, ss_size);
 
     // Update statistics for actual release to OS