WIP: Add TLS SLL validation and SuperSlab registry fallback

ChatGPT's diagnostic changes to address TLS_SLL_HDR_RESET issue.
Current status: Partial mitigation, but root cause remains.

Changes Applied:
1. SuperSlab Registry Fallback (hakmem_super_registry.h)
   - Added legacy table probe when hash map lookup misses
   - Prevents NULL returns for valid SuperSlabs during initialization
   - Status: ✅ Works but may hide underlying registration issues

2. TLS SLL Push Validation (tls_sll_box.h)
   - Reject push if SuperSlab lookup returns NULL
   - Reject push if class_idx mismatch detected
   - Added [TLS_SLL_PUSH_NO_SS] diagnostic message
   - Status: ✅ Prevents list corruption (defensive)

3. SuperSlab Allocation Class Fix (superslab_allocate.c)
   - Pass actual class_idx to sp_internal_allocate_superslab
   - Prevents dummy class=8 causing OOB access
   - Status: ✅ Root cause fix for allocation path

4. Debug Output Additions
   - First 256 push/pop operations traced
   - First 4 mismatches logged with details
   - SuperSlab registration state logged
   - Status: ✅ Diagnostic tool (not a fix)

5. TLS Hint Box Removed
   - Deleted ss_tls_hint_box.{c,h} (Phase 1 optimization)
   - Simplified to focus on stability first
   - Status: ⏳ Can be re-added after root cause fixed

Current Problem (REMAINS UNSOLVED):
- [TLS_SLL_HDR_RESET] still occurs after ~60 seconds of sh8bench
- Pointer is 16 bytes offset from expected (class 1 → class 2 boundary)
- hak_super_lookup returns NULL for that pointer
- Suggests: Use-After-Free, Double-Free, or pointer arithmetic error

Root Cause Analysis:
- Pattern: Pointer offset by +16 (one class 1 stride)
- Timing: Cumulative problem (appears after 60s, not immediately)
- Location: Header corruption detected during TLS SLL pop

Remaining Issues:
⚠️ Registry fallback is defensive (may hide registration bugs)
⚠️ Push validation prevents symptoms but not root cause
⚠️ 16-byte pointer offset source unidentified

Next Steps for Investigation:
1. Full pointer arithmetic audit (Magazine ⇔ TLS SLL paths)
2. Enhanced logging at HDR_RESET point:
   - Expected vs actual pointer value
   - Pointer provenance (where it came from)
   - Allocation trace for that block
3. Verify Headerless flag is OFF throughout build
4. Check for double-offset application in conversions

Technical Assessment:
- 60% root cause fixes (allocation class, validation)
- 40% defensive mitigation (registry fallback, push rejection)

Performance Impact:
- Registry fallback: +10-30 cycles on cold path (negligible)
- Push validation: +5-10 cycles per push (acceptable)
- Overall: < 2% performance impact estimated

Related Issues:
- Phase 1 TLS Hint Box removed temporarily
- Phase 2 Headerless blocked until stability achieved

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

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

core/box/hak_core_init.inc.h

@@ -37,6 +37,7 @@ void hak_init(void) {
 }
 
 static void hak_init_impl(void) {
+    HAK_TRACE("[init_impl_enter]\n");
     g_init_thread = pthread_self();
     atomic_store_explicit(&g_initializing, 1, memory_order_release);
 
@@ -44,6 +45,7 @@ static void hak_init_impl(void) {
     // This MUST be called before ANY allocation (Tiny/Mid/Large/Learner)
     // dlsym() initializes function pointers to real libc (bypasses LD_PRELOAD)
     hkm_syscall_init();
+    HAK_TRACE("[init_impl_after_syscall_init]\n");
 
     // CRITICAL FIX (BUG #10): Pre-detect jemalloc ONCE during init, not on hot path!
     // This prevents infinite recursion: malloc → hak_jemalloc_loaded → dlopen → malloc → ...
@@ -58,6 +60,7 @@ static void hak_init_impl(void) {
             HAKMEM_LOG("Detected jemalloc: will avoid interposing\n");
         }
     }
+    HAK_TRACE("[init_impl_after_jemalloc_probe]\n");
 
     // Optional: one-shot SIGSEGV backtrace for early crash diagnosis
     do {