Phase 35-39: FAST build optimization complete (+7.13% cumulative)

Phase 35-A: BENCH_MINIMAL gate function elimination (GO +4.39%)
- tiny_front_v3_enabled() → constant true
- tiny_metadata_cache_enabled() → constant 0
- learner_v7_enabled() → constant false
- small_learner_v2_enabled() → constant false

Phase 36: Policy snapshot init-once (GO +0.71%)
- small_policy_v7_snapshot() version check skip in BENCH_MINIMAL
- TLS cache for policy snapshot

Phase 37: Standard TLS cache (NO-GO -0.07%)
- TLS cache for Standard build attempted
- Runtime gate overhead negates benefit

Phase 38: FAST/OBSERVE/Standard workflow established
- make perf_fast, make perf_observe targets
- Scorecard and documentation updates

Phase 39: Hot path gate constantization (GO +1.98%)
- front_gate_unified_enabled() → constant 1
- alloc_dualhot_enabled() → constant 0
- g_bench_fast_front, g_v3_enabled blocks → compile-out
- free_dispatch_stats_enabled() → constant false

Results:
- FAST v3: 56.04M ops/s (47.4% of mimalloc)
- Standard: 53.50M ops/s (45.3% of mimalloc)
- M1 target (50%): 5.5% remaining

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

core/box/hak_free_api.inc.h

@@ -3,6 +3,7 @@
 #ifndef HAK_FREE_API_INC_H
 #define HAK_FREE_API_INC_H
 
+#include "../hakmem_build_flags.h"  // Phase 39: HAKMEM_BENCH_MINIMAL (GO +1.98%)
 #include <sys/mman.h>  // For mincore() in AllocHeader safety check
 #include "hakmem_tiny_superslab.h"  // For SUPERSLAB_MAGIC, SuperSlab
 #include "../ptr_trace.h"              // Debug: pointer trace immediate dump on libc fallback
@@ -112,6 +113,8 @@ void hak_free_at(void* ptr, size_t size, hak_callsite_t site) {
 #endif
     // Bench-only ultra-short path: try header-based tiny fast free first
     // Enable with: HAKMEM_BENCH_FAST_FRONT=1
+    // Phase 39: BENCH_MINIMAL → compile-out (GO +1.98%)
+#if !HAKMEM_BENCH_MINIMAL
     {
         static int g_bench_fast_front = -1;
         if (__builtin_expect(g_bench_fast_front == -1, 0)) {
@@ -129,6 +132,7 @@ void hak_free_at(void* ptr, size_t size, hak_callsite_t site) {
         }
 #endif
     }
+#endif
 
     if (!ptr) {
 #if HAKMEM_DEBUG_TIMING
@@ -168,7 +172,8 @@ void hak_free_at(void* ptr, size_t size, hak_callsite_t site) {
         case FG_DOMAIN_TINY: {
             // Phase FREE-FRONT-V3-2: v3 snapshot routing (optional, default OFF)
             // Optimized: No tiny_route_for_class() calls, no redundant ENV checks
-#if HAKMEM_TINY_HEADER_CLASSIDX
+            // Phase 39: BENCH_MINIMAL → compile-out (GO +1.98%)
+#if HAKMEM_TINY_HEADER_CLASSIDX && !HAKMEM_BENCH_MINIMAL
             {
                 // Check if v3 snapshot routing is enabled (cached)
                 static int g_v3_enabled = -1;