Phase 68: PGO training set diversification (seed/WS expansion)

Changes:
- scripts/box/pgo_fast_profile_config.sh: Expanded WS patterns (3→5) and seeds (1→3)
  for reduced overfitting and better production workload representativeness
- PERFORMANCE_TARGETS_SCORECARD.md: Phase 68 baseline promoted (61.614M = 50.93%)
- CURRENT_TASK.md: Phase 68 marked complete, Phase 67a (layout tax forensics) set Active

Results:
- 10-run verification: +1.19% vs Phase 66 baseline (GO, >+1.0% threshold)
- M1 milestone: 50.93% of mimalloc (target 50%, exceeded by +0.93pp)
- Stability: 10-run mean/median with <2.1% CV

🤖 Generated with Claude Code

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

core/box/fastlane_direct_env_box.h

@@ -19,6 +19,7 @@
 
 #include <stdatomic.h>
 #include <stdlib.h>
+#include "../hakmem_build_flags.h"
 
 // ENV control: cached flag for fastlane_direct_enabled()
 // -1: uninitialized, 0: disabled, 1: enabled
@@ -30,6 +31,9 @@ extern _Atomic int g_fastlane_direct_enabled;
 // Returns: 1 if enabled, 0 if disabled
 // Hot path: Single atomic load (after first call)
 static inline int fastlane_direct_enabled(void) {
+#if HAKMEM_FAST_PROFILE_FIXED
+    return 1;
+#endif
     int val = atomic_load_explicit(&g_fastlane_direct_enabled, memory_order_relaxed);
     if (__builtin_expect(val == -1, 0)) {
         // Cold path: Initialize from ENV