Phase 4c: Add master trace control (HAKMEM_TRACE)

Add unified trace control that allows enabling specific trace modules
using comma-separated values or "all" to enable everything.

New file: core/hakmem_trace_master.h
- HAKMEM_TRACE=all: Enable all trace modules
- HAKMEM_TRACE=ptr,refill,free,mailbox: Enable specific modules
- HAKMEM_TRACE_LEVEL=N: Set trace verbosity (1-3)
- hak_trace_check(): Check if module should enable tracing

Available trace modules:
  ptr, refill, superslab, ring, free, mailbox, registry

Priority order:
1. HAKMEM_QUIET=1 → suppress all
2. Specific module ENV (e.g., HAKMEM_PTR_TRACE=1)
3. HAKMEM_TRACE=module1,module2
4. Default → disabled

Updated files:
- core/tiny_refill.h: Use hak_trace_check() for refill tracing
- core/box/mailbox_box.c: Use hak_trace_check() for mailbox tracing

Performance: No regression (72.9M ops/s)

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

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

core/tiny_refill.h

@@ -2,6 +2,7 @@
 #pragma once
 #include <stdatomic.h>
 #include "hakmem_tiny_superslab.h"
+#include "hakmem_trace_master.h"  // Phase 4c: Master trace control
 #include "slab_handle.h"
 #include "tiny_sticky.h"
 #include "tiny_ready.h"
@@ -86,13 +87,13 @@ static inline SuperSlab* tiny_refill_try_fast(int class_idx, TinyTLSSlab* tls) {
             }
         }
     }
-    // One-shot entry trace (env: HAKMEM_TINY_RF_TRACE), disabled in release builds
+    // One-shot entry trace (env: HAKMEM_TINY_RF_TRACE or HAKMEM_TRACE=refill)
+    // Phase 4c: Now uses hak_trace_check() for unified trace control
 #if !HAKMEM_BUILD_RELEASE
     do {
         static int en = -1; static _Atomic int printed[8];
         if (__builtin_expect(en == -1, 0)) {
-            const char* e = getenv("HAKMEM_TINY_RF_TRACE");
-            en = (e && atoi(e) != 0) ? 1 : 0;
+            en = hak_trace_check("HAKMEM_TINY_RF_TRACE", "refill");
         }
         if (en) {
             int expected = 0;