docs(joinir): Phase 47 - Normalized P3 (If-Sum) design

Complete design for extending Normalized JoinIR to Pattern3 (if-sum) loops,
reusing 90% of existing P2 infrastructure.

Key insight: P3 already uses P2's Structured JoinIR foundation (Phase 220
ConditionEnv integration), so Normalized extension is straightforward.

Design documents:
- phase47-norm-p3-design.md: Complete P3 Normalized design
  - Infrastructure reuse analysis (ConditionEnv, CarrierInfo, ExitLine)
  - Representative loops identified (phase212_if_sum_min primary target)
  - StepScheduleBox extension (IfCond, ThenUpdates, ElseUpdates)
  - JpInst reuse (If instruction already exists)
  - Implementation strategy (dev-only → canonical)
  - File impact estimate (~365 lines, pure additive)

- phase47-test-files-inventory.md: P3 test file catalog
  - 3 P3 test files analyzed
  - phase212_if_sum_min.hako: Single carrier (PRIMARY)
  - phase217_if_sum_multi_min.hako: Multi-carrier (sum + count)
  - phase218_json_if_sum_min.hako: Variable accumulation (sum + i)

Architecture:
- Unified Normalized for P1/P2/P3 (same pipeline)
- Conditional updates only difference vs P2
- No P2 code changes needed (pure additive)

Benefits:
- 90% infrastructure reuse from P2
- Proven incremental rollout (dev → canonical)
- Clear path to P4 (continue pattern)

Implementation roadmap:
- Phase 47-A: Minimal sum_count (dev-only)
- Phase 47-B: array_filter (body-local + method calls)
- Phase 47-C: Canonical promotion

Updates:
- joinir-architecture-overview.md: Added Phase 47 section
- CURRENT_TASK.md: Updated Phase 47 entry (Design Complete)

Status: Design phase complete, ready for implementation

docs/development/current/main/joinir-architecture-overview.md

@@ -1358,3 +1358,25 @@ JsonParser _skip_whitespace / _atoi / _parse_number が**すべて canonical Nor
 - `normalized_joinir_min.rs`: canonical set 検証テスト追加
 
 **テスト**: 937/937 PASS
+
+### 3.24 Phase 47-NORM-P3 – Normalized P3 (If-Sum) Support 🏗️ DESIGN (2025-12-12)
+
+**設計詳細**: [phase47-norm-p3-design.md](./phase47-norm-p3-design.md)
+
+Pattern3 (if-sum) ループを Normalized JoinIR に対応させる。P2 と同じ ConditionEnv/CarrierInfo/ExitLine インフラを再利用。
+
+**Phase 220 基盤**: P3 if-sum は Phase 220 で ConditionEnv 統合済み（既に P2 と同じ Structured JoinIR foundation を持つ）
+
+**Key difference**: P3 は **conditional carrier updates**（if 内でのみキャリア更新）vs P2 の unconditional updates before break
+
+**Phase 47-A**: Minimal sum_count (dev-only Normalized)
+- ✅ EnvLayout: P2 と同じ構造（carrier フィールド）
+- ✅ StepScheduleBox: `IfCond`, `ThenUpdates`, `ElseUpdates` ステップ追加
+- ✅ JpInst: 既存の `If` 命令を再利用
+- 🎯 Test: `phase212_if_sum_min.hako` → Normalized→MIR(direct) 検証
+
+**Phase 47-B**: array_filter (dev-only, body-local + method calls)
+
+**Phase 47-C**: Canonical promotion (P3 minimal → canonical)
+
+**スコープ外**: P4 (continue) 対応（NORM-P4 フェーズで実施）、Complex P3 patterns（後続フェーズ）