docs(joinir): Phase 48 - Normalized P4 (Continue) design

Complete design documentation for Pattern4 (continue) Normalized support,
extending unified Normalized infrastructure to all 4 loop patterns.

Design documents:
- phase48-norm-p4-design.md: Complete P4 Normalized design (380 lines)
  - Key insight: continue = immediate TailCallFn(loop_step, ...) (no new instruction!)
  - Infrastructure reuse: 95%+ from P2/P3 (only ContinueCheck step kind new)
  - Target loops prioritized:
    - ◎ _parse_array (skip whitespace) - PRIMARY (Phase 48-A)
    - ○ _parse_object (skip whitespace) - Extended
    - △ _unescape_string, _parse_string - Later
  - Control flow: ContinueCheck before Updates (skip processing early)
  - Same EnvLayout/ConditionEnv/CarrierInfo/ExitLine as P2/P3
  - Implementation strategy: dev-only → canonical (proven approach)

Architecture:
- Unified Normalized for P1/P2/P3/P4 (all patterns same pipeline)
- P4 uses loop_step(env, k_exit) skeleton (same as P2/P3)
- continue semantics: TailCallFn = skip to next iteration (CPS natural fit)

Benefits:
- 95% infrastructure reuse from P2/P3
- No new JpInst needed (continue = existing TailCallFn)
- Incremental rollout (dev → canonical)
- Clear semantic: continue = immediate recursion

Implementation roadmap:
- Phase 48-A: Minimal continue (dev-only)
- Phase 48-B: Extended patterns (multi-carrier)
- Phase 48-C: Canonical promotion

Updates:
- joinir-architecture-overview.md: Added Phase 48 section
- CURRENT_TASK.md: Phase 48 entry (Design Complete)
- phase47-norm-p3-design.md: Minor formatting

Status: Design phase complete (doc-only, no implementation yet)
Next: Phase 48-A implementation (when requested)

docs/development/current/main/phase47-norm-p3-design.md

@@ -165,38 +165,36 @@ Complex P3 patterns from selfhost compiler (deferred to later phase).
 **Phase 47-A-IMPL** (✅ Complete, 2025-12-12):
 - ✅ StepSchedule renamed and extended: `pattern2_step_schedule.rs` → `step_schedule.rs`
 - ✅ P3 StepKind added: `IfCond`, `ThenUpdates`, `ElseUpdates`
-- ✅ Pattern2 lowering separation: P3 steps panic in P2 lowering (clean boundary)
-- ✅ ShapeGuard: `Pattern3IfSumMinimal` detection added (placeholder stub)
-- ✅ Normalized bridge: P3 shape handling in `normalize_for_shape()` and roundtrip
-- ✅ 938/938 tests PASS (no regressions)
-- ⏳ TODO: Full P3 Normalized lowering (Phase 47-A-LOWERING)
+- ✅ Pattern2 lowering separation: P3 steps panic in P2 lowering（責務境界を明確化）
+- ✅ ShapeGuard: `Pattern3IfSumMinimal` detection added（構造ベース検出）
+- ✅ Normalized bridge: `normalize_pattern3_if_sum_minimal` を通じて P3 最小ケースを Normalized→MIR(direct) パイプラインに統合
+- ✅ Runner / VM tests: P3 minimal について Structured 経路と Normalized→MIR(direct) 経路が一致することを dev-only スイートで確認
+- ✅ 938/938 tests PASS（退行なし）
 
-**Next Phase** (Phase 47-A-LOWERING):
-- Implement `lower_pattern3_if_sum_minimal()` fully
-- Generate Normalized JpInst for P3 structure (If branching, conditional updates)
-- Test VM output comparison (Normalized vs Structured)
+**Next Phase**（Phase 47-B 以降）:
+- array_filter など body-local + method call を含む P3 ループへの適用
+- multi-carrier if-sum（sum + count）や JsonParser 由来 P3 への拡張
+- Canonical 昇格（P3 minimal を dev-only から常時 Normalized 経路へ）
 
 ## Implementation Strategy
 
-### Phase 47-A: Minimal sum_count (dev-only)
+### Phase 47-A: Minimal sum_count (dev-only, 実装済みの範囲)
 
 **Goal**: Prove P3 can use Normalized infrastructure with minimal additions.
 
-**Steps**:
-1. **ShapeGuard**: Add `Pattern3IfSumMinimal` shape
-2. **StepScheduleBox**: Add `ConditionalUpdate` step kind
-3. **Normalized lowering**:
-   - Generate `If` JpInst for body if-statement
-   - Emit carrier updates in then/else branches
-4. **Test**: Verify Structured→Normalized→MIR(direct) matches Structured→MIR
+**実装済みステップ**:
+1. **ShapeGuard**: `Pattern3IfSumMinimal` shape 追加
+   - Compare + Select + tail call を持つ 3 関数構成の P3 if-sum 最小パターンを検出。
+2. **StepScheduleBox**: P3 用 StepKind 追加
+   - `IfCond` / `ThenUpdates` / `ElseUpdates` を `step_schedule.rs` に導入し、P2/P3 共通の箱として再利用。
+3. **Normalized lowering（minimal）**:
+   - `normalize_pattern3_if_sum_minimal` により、P3 最小ケースを P2 と同じ器の NormalizedModule に変換し、direct ブリッジで扱える形に整備。
+4. **Tests**:
+   - Runner 経路: `normalized_pattern3_if_sum_minimal_runner_dev_switch_matches_structured`
+   - Normalization 経路: `test_phase47a_pattern3_if_sum_minimal_normalization`（shape + normalize 成功）
+   - （詳細な VM Bridge 比較は Phase 47-B 以降で拡張していく）
 
-**Expected additions**:
-- `shape_guard.rs`: +1 shape variant
-- `pattern2_step_schedule.rs`: Rename to `step_schedule.rs`, add P3 support
-- `normalized_bridge/direct.rs`: Handle `If` JpInst with carrier updates
-- `tests/normalized_joinir_min.rs`: +1 P3 test
-
-**Dev fixture**: `phase212_if_sum_min.hako` → `jsonparser_if_sum_minimal`
+**Dev fixture**: `apps/tests/phase212_if_sum_min.hako`（最小 if-sum パターン）
 
 ### Phase 47-B: array_filter (dev-only)