docs(phase131): Phase 131-3 完了 - LLVM lowering 棚卸し（3ケース）

Phase 131-3 完了: MIR→LLVM lowering 棚卸し

テスト結果マトリックス:
- Case A (phase87_llvm_exe_min.hako): ✅ PASS (baseline)
- Case B (loop_min_while.hako): ❌ TAG-EMIT (PHI after terminator)
- Case B2 (print(42) simple): ✅ PASS (BoxCall works)
- Case C (llvm_stage3_loop_only.hako): ❌ TAG-EMIT (JoinIR pattern gap)

Critical Bugs:
1. Bug #1: PHI After Terminator (Case B)
   - 原因: function_lower.py が terminator を PHI より先に emit
   - 修正: 4-pass block emission (2-3h)

2. Bug #2: JoinIR Pattern Gap (Case C)
   - 原因: loop(true) { break } パターンが JoinIR 未対応
   - 修正: Pattern 5 設計・実装 (3-4h)

Next Actions:
- P1 (推奨): PHI ordering 修正 → 80% のループを有効化
- P2: JoinIR Pattern 5 → infinite loop 対応

ドキュメント:
- phase131-3-llvm-lowering-inventory.md: 詳細棚卸し結果
- phase87-selfhost-llvm-exe-line.md: LLVM IR parsing error 追記
- CURRENT_TASK.md: phase131-3 参照追加

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

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

CURRENT_TASK.md

@@ -30,6 +30,8 @@
 - `docs/development/current/main/phase81-pattern2-exitline-contract.md`
 - `docs/development/current/main/phase78-85-boxification-feedback.md`
 - `docs/development/current/main/phase87-selfhost-llvm-exe-line.md`
+- `docs/development/current/main/phase131-2-box-resolution-map.md`
+- `docs/development/current/main/phase131-3-llvm-lowering-inventory.md`
 
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