Phase 83-1 + Allocator Comparison: Switch dispatch fixed (NO-GO +0.32%), PROFILE correction, SCORECARD update

Key changes:
- Phase 83-1: Switch dispatch fixed mode (tiny_inline_slots_switch_dispatch_fixed_box) - NO-GO (marginal +0.32%, branch reduction negligible)
  Reason: lazy-init pattern already optimal, Phase 78-1 pattern shows diminishing returns

- Allocator comparison baseline update (10-run SSOT, WS=400, ITERS=20M):
  tcmalloc: 115.26M (92.33% of mimalloc)
  jemalloc: 97.39M (77.96% of mimalloc)
  system: 85.20M (68.24% of mimalloc)
  mimalloc: 124.82M (baseline)

- hakmem PROFILE correction: scripts/run_mixed_10_cleanenv.sh + run_allocator_quick_matrix.sh
  PROFILE explicitly set to MIXED_TINYV3_C7_SAFE for hakmem measurements
  Result: baseline stabilized to 55.53M (44.46% of mimalloc)
  Previous unstable measurement (35.57M) was due to profile leak

- Documentation:
  * PERFORMANCE_TARGETS_SCORECARD.md: Reference allocators + M1/M2 milestone status
  * PHASE83_1_SWITCH_DISPATCH_FIXED_RESULTS.md: Phase 83-1 analysis (NO-GO)
  * ALLOCATOR_COMPARISON_QUICK_RUNBOOK.md: Quick comparison procedure
  * ALLOCATOR_COMPARISON_SSOT.md: Detailed SSOT methodology

- M2 milestone status: 44.46% (target 55%, gap -10.54pp) - structural improvements needed

🤖 Generated with Claude Code
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

core/front/tiny_c6_inline_slots.h

@@ -24,6 +24,7 @@
 #include <stdint.h>
 #include "../box/tiny_c6_inline_slots_env_box.h"
 #include "../box/tiny_c6_inline_slots_tls_box.h"
+#include "../box/tiny_inline_slots_fixed_mode_box.h"
 
 // ============================================================================
 // Fast-Path API (always_inline for zero branch overhead)
@@ -75,8 +76,7 @@ static inline TinyC6InlineSlots* c6_inline_tls(void) {
 // Check if C6 inline is enabled AND initialized (combined gate)
 // Returns: 1 if ready to use, 0 if disabled or uninitialized
 static inline int c6_inline_ready(void) {
-    // ENV gate first (cached, zero cost after first call)
-    if (!tiny_c6_inline_slots_enabled()) {
+    if (!tiny_c6_inline_slots_enabled_fast()) {
         return 0;
     }