Cleanup: Consolidate debug ENV vars to HAKMEM_DEBUG_LEVEL

Integrated 4 new debug environment variables added during bug fixes
into the existing unified HAKMEM_DEBUG_LEVEL system (expanded to 0-5 levels).

Changes:

1. Expanded HAKMEM_DEBUG_LEVEL from 0-3 to 0-5 levels:
   - 0 = OFF (production)
   - 1 = ERROR (critical errors)
   - 2 = WARN (warnings)
   - 3 = INFO (allocation paths, header validation, stats)
   - 4 = DEBUG (guard instrumentation, failfast)
   - 5 = TRACE (verbose tracing)

2. Integrated 4 environment variables:
   - HAKMEM_ALLOC_PATH_TRACE → HAKMEM_DEBUG_LEVEL >= 3 (INFO)
   - HAKMEM_TINY_SLL_VALIDATE_HDR → HAKMEM_DEBUG_LEVEL >= 3 (INFO)
   - HAKMEM_TINY_REFILL_FAILFAST → HAKMEM_DEBUG_LEVEL >= 4 (DEBUG)
   - HAKMEM_TINY_GUARD → HAKMEM_DEBUG_LEVEL >= 4 (DEBUG)

3. Kept 2 special-purpose variables (fine-grained control):
   - HAKMEM_TINY_GUARD_CLASS (target class for guard)
   - HAKMEM_TINY_GUARD_MAX (max guard events)

4. Backward compatibility:
   - Legacy ENV vars still work via hak_debug_check_level()
   - New code uses unified system
   - No behavior changes for existing users

Updated files:
- core/hakmem_debug_master.h (level 0-5 expansion)
- core/hakmem_tiny_superslab_internal.h (alloc path trace)
- core/box/tls_sll_box.h (header validation)
- core/tiny_failfast.c (failfast level)
- core/tiny_refill_opt.h (failfast guard)
- core/hakmem_tiny_ace_guard_box.inc (guard enable)
- core/hakmem_tiny.c (include hakmem_debug_master.h)

Impact:
- Simpler debug control: HAKMEM_DEBUG_LEVEL=3 instead of 4 separate ENVs
- Easier to discover/use
- Consistent debug levels across codebase
- Reduces ENV variable proliferation (43+ vars surveyed)

Future work:
- Consolidate remaining 39+ debug variables (documented in survey)
- Gradual migration over 2-3 releases

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

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

core/box/tls_sll_box.h

@@ -26,6 +26,7 @@
 
 #include "../hakmem_tiny_config.h"
 #include "../hakmem_build_flags.h"
+#include "../hakmem_debug_master.h"  // For unified debug level control
 #include "../tiny_remote.h"
 #include "../tiny_region_id.h"
 #include "../hakmem_tiny_integrity.h"
@@ -296,15 +297,15 @@ static inline bool tls_sll_push_impl(int class_idx, void* ptr, uint32_t capacity
 
 #if HAKMEM_TINY_HEADER_CLASSIDX
     // Validate header on push - detect blocks pushed without header write
-    // Enabled via HAKMEM_TINY_SLL_VALIDATE_HDR=1 or in debug builds
+    // Enabled via HAKMEM_DEBUG_LEVEL >= 3 (INFO level) or in debug builds
+    // Legacy: HAKMEM_TINY_SLL_VALIDATE_HDR=1 still works for compatibility
     do {
         static int g_validate_hdr = -1;
         if (__builtin_expect(g_validate_hdr == -1, 0)) {
 #if !HAKMEM_BUILD_RELEASE
             g_validate_hdr = 1;  // Always on in debug
 #else
-            const char* env = getenv("HAKMEM_TINY_SLL_VALIDATE_HDR");
-            g_validate_hdr = (env && *env && *env != '0') ? 1 : 0;
+            g_validate_hdr = hak_debug_check_level("HAKMEM_TINY_SLL_VALIDATE_HDR", 3);
 #endif
         }