feat(joinir): Phase 286 P3.2 - Pattern5 Plan line (loop(true) + early exit)

- Pattern5InfiniteEarlyExitPlan (Return/Break variants)
- extract_pattern5_plan() for loop(true) literal only
- normalize_pattern5_return(): 5 blocks CFG (header→body→found/step)
- normalize_pattern5_break(): 6 blocks CFG with carrier PHI
- NormalizationPlanBox exclusion for Pattern5-style loops
- Fixtures: phase286_pattern5_{return,break}_min.hako
- quick smoke 154/154 PASS

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

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

docs/development/current/main/phases/phase-286/README.md

@@ -1,6 +1,6 @@
 # Phase 286: JoinIR Line Absorption（JoinIR→CorePlan/Frag 収束）
 
-Status: In Progress (P0, P1, P2, P2.1, P2.2, P2.3, P2.4, P2.4.1, P2.6, P2.7, P3, 286C-2, **P3.1 COMPLETE**)
+Status: ✅ COMPLETE (P0, P1, P2, P2.1, P2.2, P2.3, P2.4.1, P2.6, P2.7, P2.8, P3.1, P3.2, P3 COMPLETE)
 
 ## Goal
 
@@ -38,8 +38,22 @@ Phase 286 では JoinIR line を “第2の lowerer” として放置せず、*
 
 ## Next（短期の道筋）
 
-- **P2.6.1（Pattern3 Plan完走）**: `docs/development/current/main/phases/phase-286/P2.6.1-INSTRUCTIONS.md`
 - **将来設計の相談（別フェーズでSSOT化してから）**: `docs/development/current/main/investigations/phase-286-plan-normalization-consult.md`
+- **次のおすすめ（design-first）**: Phase 284（Return as ExitKind SSOT）
+
+## Coverage Map（Plan line 移行状況）
+
+| Pattern | Shape | Status | Notes |
+|---:|---|---|---|
+| 1 | SimpleWhile | ✅ Plan line | PoC + integration fixture固定済み |
+| 2 | Break | ✅ Plan line | PoCサブセットは Plan 完走、PoC外は `Ok(None)` で legacy fallback |
+| 3 | If-Phi | ✅ Plan line | Fail-Fast 統一（extract `Some` 後の legacy fallback なし） |
+| 4 | Continue | ✅ Plan line | PoC + integration fixture固定済み |
+| 5 | InfiniteEarlyExit | ✅ Plan line | `loop(true)` literal に限定した PoC サブセット（Return/Break） |
+| 6 | ScanWithInit | ✅ Plan line | Phase 273 で SSOT |
+| 7 | SplitScan | ✅ Plan line | Phase 273 で SSOT |
+| 8 | BoolPredicateScan | ✅ Plan line | static box は設計上スキップ（ReceiverNormalizeBox が担当） |
+| 9 | AccumConstLoop | ✅ Plan line | Pattern1 より優先（より具体的） |
 
 ### P0（docs-only）✅ COMPLETE (2025-12-25)
 
@@ -380,6 +394,67 @@ preheader → header(PHI: i_current, carrier_current)
 - ✅ Fixture B (break without update): Plan line PASS (出力 11)
 - ✅ Regression: quick smoke 154 PASS, 0 FAILED
 
+### P3.2 (Pattern5 Plan化 - Infinite Loop with Early Exit) ✅ COMPLETE (2025-12-26)
+
+**完了内容**:
+- Pattern5InfiniteEarlyExitPlan 追加（Return版・Break版両対応）
+- extract_pattern5_plan() 実装（loop(true) リテラル限定）
+- normalize_pattern5_infinite_early_exit() 実装（Return版5blocks、Break版6blocks CFG）
+- NormalizationPlanBox で Pattern5 スタイルループを除外（Plan line へルーティング）
+- quick smoke 154/154 PASS
+
+**背景**:
+- Pattern5 は `loop(true)` の無限ループパターン
+- 既存 legacy Pattern5 は `break + continue` 両方必須の複雑な形式
+- PoC は **simpler subset**: 早期 return または break 単独
+
+**CFG構造（Return版）**:
+```
+preheader → header(PHI: i_current) → body(exit_cond)
+              ↑                           ↓
+              └───── step ←────────  else path
+                                          ↓
+                               then path: CoreExitPlan::Return
+```
+
+**CFG構造（Break版）**:
+```
+preheader → header(PHI: i, carrier) → body(exit_cond)
+              ↑                             ↓
+              └───── step ←──────────  else path
+                                            ↓
+                                 then path → after_bb(PHI: carrier_out)
+```
+
+**実装ステップ**:
+1. Step 0: docs-first - README P3.2節追加
+2. Step 1: integration fixture 2本 (return版、break版)
+3. Step 2: DomainPlan::Pattern5InfiniteEarlyExit 追加
+4. Step 3: extract_pattern5_plan() 実装
+5. Step 4: normalize_pattern5_infinite_early_exit() 実装
+6. Step 5: router に Pattern5 追加
+7. Step 6: 検証
+
+**PoC サブセット厳守**:
+- `loop(true)` リテラルのみ（`loop(1)` や truthy は `Ok(None)`）
+- Return版: `if (cond) { return <expr> }` + `i = i + 1`
+- Break版: `if (cond) { break }` + `sum = sum + 1` + `i = i + 1`（carrier_update 必須）
+
+**成果物** (予定):
+- `apps/tests/phase286_pattern5_return_min.hako` (Fixture A)
+- `apps/tests/phase286_pattern5_break_min.hako` (Fixture B)
+- `tools/smokes/v2/profiles/integration/apps/phase286_pattern5_return_vm.sh`
+- `tools/smokes/v2/profiles/integration/apps/phase286_pattern5_break_vm.sh`
+- `src/mir/builder/control_flow/plan/mod.rs` (Pattern5InfiniteEarlyExitPlan + Pattern5ExitKind)
+- `src/mir/builder/control_flow/joinir/patterns/extractors/pattern5.rs` (extract_pattern5_plan)
+- `src/mir/builder/control_flow/plan/normalizer.rs` (normalize_pattern5_infinite_early_exit)
+- `src/mir/builder/control_flow/joinir/patterns/router.rs` (Pattern5 Plan line routing)
+
+**成功基準**:
+- Fixture A (return): PASS (出力 7)
+- Fixture B (break): PASS (出力 3)
+- Regression: quick smoke 154 PASS, 0 FAILED
+
 ## Acceptance（P0）
 
 - 2本の lowering が "設計として" どこで 1 本に収束するかが明文化されている