feat(llvm): Phase 132 - Pattern 1 exit value parity fix + Box-First refactoring

## Phase 132: Exit PHI Value Parity Fix

### Problem
Pattern 1 (Simple While) returned 0 instead of final loop variable value (3)
- VM: RC: 3 ✅ (correct)
- LLVM: Result: 0 ❌ (wrong)

### Root Cause (Two Layers)
1. **JoinIR/Boundary**: Missing exit_bindings → ExitLineReconnector not firing
2. **LLVM Python**: block_end_values snapshot dropping PHI values

### Fix
**JoinIR** (simple_while_minimal.rs):
- Jump(k_exit, [i_param]) passes exit value

**Boundary** (pattern1_minimal.rs):
- Added LoopExitBinding with carrier_name="i", role=LoopState
- Enables ExitLineReconnector to update variable_map

**LLVM** (block_lower.py):
- Use predeclared_ret_phis for reliable PHI filtering
- Protect builder.vmap PHIs from overwrites (SSOT principle)

### Result
- ✅ VM: RC: 3
- ✅ LLVM: Result: 3
- ✅ VM/LLVM parity achieved

## Phase 132-Post: Box-First Refactoring

### Rust Side
**JoinModule::require_function()** (mod.rs):
- Encapsulate function search logic
- 10 lines → 1 line (90% reduction)
- Reusable for Pattern 2-5

### Python Side
**PhiManager Box** (phi_manager.py - new):
- Centralized PHI lifecycle management
- 47 lines → 8 lines (83% reduction)
- SSOT: builder.vmap owns PHIs
- Fail-Fast: No silent overwrites

**Integration**:
- LLVMBuilder: Added phi_manager
- block_lower.py: Delegated to PhiManager
- tagging.py: Register PHIs with manager

### Documentation
**New Files**:
- docs/development/architecture/exit-phi-design.md
- docs/development/current/main/investigations/phase132-llvm-exit-phi-wrong-result.md
- docs/development/current/main/phases/phase-132/

**Updated**:
- docs/development/current/main/10-Now.md
- docs/development/current/main/phase131-3-llvm-lowering-inventory.md

### Design Principles
- Box-First: Logic encapsulated in classes/methods
- SSOT: Single Source of Truth (builder.vmap for PHIs)
- Fail-Fast: Early explicit failures, no fallbacks
- Separation of Concerns: 3-layer architecture

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

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

docs/development/current/main/10-Now.md

@@ -1,5 +1,14 @@
 # Self Current Task — Now (main)
 
+## 2025‑12‑15：Phase 132 完了 ✅
+
+**Phase 132: LLVM Exit PHI=0 根治修正 完了！**
+- ループ exit PHI が 0 を返す問題を根治解決
+- 原因（2層）: (1) JoinIR/Boundary が exit 値を境界に渡していない、(2) LLVM Python が PHI を落とす/上書きする
+- 修正: Pattern 1 で exit 値を明示的に渡す + `predeclared_ret_phis` 使用 + `builder.vmap` の PHI 保護
+- 結果: `/tmp/p1_return_i.hako` が 3 を返す（VM 一致）
+- 詳細: `investigations/phase132-llvm-exit-phi-wrong-result.md`
+
 ## 2025‑12‑14：現状サマリ
 
 （補足）docs が増えて迷子になったときの「置き場所ルール（SSOT）」:
@@ -79,7 +88,8 @@
   - `docs/development/current/main/phase131-2-box-resolution-map.md`
 - LLVM（Python llvmlite）lowering の棚卸し（Phase 131-3..10）:
   - `docs/development/current/main/phase131-3-llvm-lowering-inventory.md`
-  - 状態: Case B（Pattern1/loop_min_while）は EMIT/LINK/RUN まで復旧済み。残りは Case C の JoinIR ループパターン穴。
+  - 状態: Case B（Pattern1/loop_min_while）は EMIT/LINK/RUN まで復旧済み。Phase 132 で `return i` の VM/LLVM parity を固定。
+  - Case C は別途 “Case C docs” を SSOT にして追跡する（状況は更新されるので、この箇所では断定しない）
   - Case C の調査と実装計画:
     - `docs/development/current/main/phase131-11-case-c-summary.md`
     - `docs/development/current/main/case-c-infinite-loop-analysis.md`