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/hakmem_env_snapshot_box.h

@@ -60,7 +60,8 @@ extern int g_hakmem_env_snapshot_ctor_mode;
 // ENV gate: default OFF (research box, set =1 to enable)
 // E3-4: Dual-mode - constructor init (fast) or legacy lazy init (fallback)
 // Phase 18 v2: BENCH_MINIMAL conditional (constant return when HAKMEM_BENCH_MINIMAL=1)
-#if HAKMEM_BENCH_MINIMAL
+// Phase 63: FAST_PROFILE_FIXED conditional (constant return for FAST profile builds)
+#if HAKMEM_BENCH_MINIMAL || HAKMEM_FAST_PROFILE_FIXED
 // In bench mode, snapshot is always enabled (one-time cost, compile-away benefit)
 static inline bool hakmem_env_snapshot_enabled(void) {
     return 1;