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/smallobject_learner_v2.c

@@ -5,6 +5,7 @@
 #include <string.h>
 #include <stdio.h>
 #include <time.h>
+#include "hakmem_build_flags.h"  // Phase 36: HAKMEM_BENCH_MINIMAL
 #include "box/smallobject_learner_v2_box.h"
 #include "box/smallobject_stats_mid_v3_box.h"
 
@@ -245,10 +246,17 @@ uint32_t small_learner_v2_retire_efficiency_pct(uint32_t class_idx) {
 // Configuration & Control
 // ============================================================================
 
+// Phase 36: BENCH_MINIMAL mode - learner is disabled (bench profiles don't use learner)
+#if HAKMEM_BENCH_MINIMAL
+bool small_learner_v2_enabled(void) {
+    return false;  // Fixed OFF in bench mode
+}
+#else
 bool small_learner_v2_enabled(void) {
     const char *env = getenv("HAKMEM_SMALL_LEARNER_V7_ENABLED");
     return (env && *env && *env != '0');
 }
+#endif
 
 void small_learner_v2_set_c5_threshold_pct(uint32_t threshold) {
     g_c5_threshold_pct = threshold;