Phase POLICY-FAST-PATH-V2 complete + MID-V35-HOTPATH-OPT-1 design

## Phase POLICY-FAST-PATH-V2 (FROZEN)
- Implementation complete: free_policy_fast_v2_box.h + malloc_tiny_fast.h integration
- A/B Results:
  - Mixed (ws=400): -1.6% regression ❌ (branch cost > skip benefit)
  - C6-heavy (ws=200): +5.4% improvement ✅
- Decision: Default OFF, FROZEN (ws<300 / C6-heavy research only)
- Learning: Large WS causes branch misprediction to dominate

## Phase 3-GRADUATE + ENV probe fix
- 64-probe retry for getenv() stability during bench_profile putenv()
- C6 ULTRA intrusive freelist: FROZEN (research box)

## Phase MID-V35-HOTPATH-OPT-1-DESIGN
- Design doc for next optimization target
- Target: MID v3.5 alloc/free hot path (C5-C6)
- Boxes: Stats Gate, TLS Layout, Boundary Check elimination
- Expected: +3-9% on Mixed mainline

Files:
- core/box/free_policy_fast_v2_box.h (new)
- core/box/free_path_stats_box.h/c (policy_fast_v2_skip counter)
- core/front/malloc_tiny_fast.h (fast-path integration)
- docs/analysis/MID_V35_HOTPATH_OPT_1_DESIGN.md (new)
- docs/analysis/PHASE_3_GRADUATE_*.md (new)
- CURRENT_TASK.md (phase status update)

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

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

core/box/free_path_stats_box.c

@@ -50,5 +50,9 @@ static void free_path_stats_dump(void) {
             g_free_path_stats.c6_ifl_pop,
             g_free_path_stats.c6_ifl_fallback);
 
+    // Phase POLICY-FAST-PATH-V2: Fast-path policy skip
+    fprintf(stderr, "[FREE_PATH_STATS_POLICY_FASTV2] skip=%lu\n",
+            g_free_path_stats.policy_fast_v2_skip);
+
     fflush(stderr);
 }