Remove legacy redundant code after Gatekeeper Box consolidation

Summary of Deletions:
- Remove core/box/unified_batch_box.c (26 lines)
  * Legacy batch allocation logic superseded by Alloc Gatekeeper Box
  * unified_cache now handles allocation aggregation

- Remove core/box/unified_batch_box.h (29 lines)
  * Header declarations for deprecated unified_batch_box module

- Remove core/tiny_free_fast.inc.h (329 lines)
  * Legacy fast-path free implementation
  * Functionality consolidated into:
    - tiny_free_gate_box.h (Fail-Fast layer + diagnostics)
    - malloc_tiny_fast.h (Free path integration)
    - unified_cache (return to freelist)
  * Code path now routes through Gatekeeper Box for consistency

Build System Updates:
- Update Makefile
  * Remove unified_batch_box.o from OBJS_BASE
  * Remove unified_batch_box_shared.o from SHARED_OBJS
  * Remove unified_batch_box.o from BENCH_HAKMEM_OBJS_BASE

- Update core/hakmem_tiny_phase6_wrappers_box.inc
  * Remove unified_batch_box references
  * Simplify allocation wrapper to use new Gatekeeper architecture

Impact:
- Removes ~385 lines of redundant/superseded code
- Consolidates allocation logic through unified Gatekeeper entry points
- All functionality preserved via new Box-based architecture
- Simplifies codebase and reduces maintenance burden

Testing:
- Build verification: make clean && make RELEASE=0/1
- Smoke tests: All pass (simple_alloc, loop 10M, pool_tls)
- No functional regressions

Rationale:
After implementing Alloc/Free Gatekeeper Boxes with Fail-Fast layers
and Unified Cache type safety, the legacy separate implementations
became redundant. This commit completes the architectural consolidation
and simplifies the allocator codebase.

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

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

core/hakmem_tiny_phase6_wrappers_box.inc

@@ -10,9 +10,6 @@
     // Box 5: Allocation Fast Path (Layer 1 - 3-4 instructions)
     #include "tiny_alloc_fast.inc.h"
 
-    // Box 6: Free Fast Path (Layer 2 - 2-3 instructions)
-    #include "tiny_free_fast.inc.h"
-
     // ---------------- Refill count (Front) global config ----------------
     // Parsed once at init; hot path reads plain ints (no getenv).
     int g_refill_count_global = 0;              // HAKMEM_TINY_REFILL_COUNT
@@ -82,19 +79,15 @@
     }
 
     void hak_tiny_free_fast_wrapper(void* ptr) {
-        // Phase E5: Ultra fast path (6-8 instruction free)
-        #if HAKMEM_ULTRA_FAST_PATH
-            tiny_free_fast_ultra(ptr);
-            return;
-        #endif
-
         static _Atomic uint64_t free_call_count = 0;
         uint64_t call_num = atomic_fetch_add(&free_call_count, 1);
         if (call_num > 14135 && call_num < 14145) {
             fprintf(stderr, "[HAK_TINY_FREE_FAST_WRAPPER] call=%lu ptr=%p\n", call_num, ptr);
             fflush(stderr);
         }
-        tiny_free_fast(ptr);
+        // Box 6 v1 (tiny_free_fast) は v2 に置き換え済み。
+        // Wrapper からは Box 経路の slow/fast 判定に委ねる。
+        hak_tiny_free(ptr);
         if (call_num > 14135 && call_num < 14145) {
             fprintf(stderr, "[HAK_TINY_FREE_FAST_WRAPPER] call=%lu completed\n", call_num);
             fflush(stderr);