Document ENV Cleanup Phase 4a completion (20 variables total)

Phase 4a: Hot Path getenv Caching - COMPLETED
- All getenv() calls in hot paths verified as properly cached
- Key fix: hakmem_elo.c (10+ loop calls → cached is_quiet())
- Verified correct caching in 7 other critical files

Added ENV_VARIABLE_SURVEY.md:
- Comprehensive survey of 228 ENV variables
- Category breakdown and consolidation recommendations
- Target: ~80 variables (65% reduction)

Updated docs/specs/ENV_VARS.md:
- Added ENV Cleanup Progress section
- Documented Phase 4a findings
- Outlined Phase 4b+ future work (HAKMEM_DEBUG/TRACE/STATS unified vars)

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

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

docs/specs/ENV_VARS.md

@@ -300,3 +300,43 @@ LD safety (for apps/LD_PRELOAD runs)
 - HAKMEM_TINY_BENCH_MODE=1
   - ベンチ専用の簡素化採用パスを有効化。per-class 単一点の公開スロットを使用し、superslab_refill のスキャンと多段リング走査を回避。
   - OOMガード（harvest/trim）は保持。A/B用途に限定してください。
+
+---
+
+ENV Cleanup Progress (2025-11)
+==============================
+
+Phase 4a: Hot Path getenv Caching
+---------------------------------
+COMPLETED: All getenv() calls in hot paths are now properly cached.
+
+Fixed files:
+- `core/hakmem_elo.c` - Added `is_quiet()` helper with cached `g_quiet_mode` flag
+  - Was: 10+ getenv("HAKMEM_QUIET") calls inside loops
+  - Now: Single cached lookup at first call
+
+Verified (already correct):
+- `core/hakmem_tiny_superslab.c` - Uses `static int g_*` caching pattern
+- `core/hakmem_shared_pool.c` - Uses `static int xxx = -1` caching
+- `core/hakmem_learner.c` - getenv outside main loop (thread start only)
+- `core/box/pool_init_api.inc.h` - Init function (called once via pthread_once)
+- `core/box/hak_core_init.inc.h` - Init function (called once via pthread_once)
+- `core/box/hak_wrappers.inc.h` - Uses `static int on=-1` caching
+
+ENV Statistics (from ENV_VARIABLE_SURVEY.md):
+- Total ENV variables: 228
+- Target after cleanup: ~80 (65% reduction)
+- Categories:
+  - Core/Toggle: 15 (7%)
+  - Learning/Adaptive: 25 (11%)
+  - Performance Tuning: 45 (20%)
+  - Debug/Diagnostic: 65 (28%) ← Consolidation target
+  - Superslab/Backend: 25 (11%)
+  - TLS SLL (P2/P3): 20 (9%)
+  - Free Path Optimization: 15 (7%)
+  - Other: 23 (10%)
+
+Future Work (Phase 4b+):
+- HAKMEM_DEBUG unified variable (consolidate 35 debug vars)
+- HAKMEM_TRACE unified variable (consolidate 15 trace vars)
+- HAKMEM_STATS unified variable (consolidate 15 dump vars)