docs: Update Phase 212.5 completion status and add Phase 213 plan

Phase 212.5 完了を記録し、Phase 213 への継続を明記。

- phase212-5-implementation-complete.md: Phase 213 への継続を追記
- CURRENT_TASK.md: Phase 212.5 完了エントリ + Phase 213 計画を追加

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

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

docs/development/current/main/phase212-5-implementation-complete.md

@@ -214,4 +214,21 @@ loop(i <= 5) {          // Actual: i <= 5 (hardcoded)
 - [x] Pattern 3 lowerer constraints documented
 - [x] Implementation report created
 
+---
+
+## 🔖 Status Update
+
+**Phase 212.5: COMPLETE ✅** (Commit: `aeb6282c`)
+
+**Scope Completed**:
+- ✅ Structural if detection (`detect_if_in_body`)
+- ✅ Pattern routing logic (classify with `has_if && carrier_count >= 1`)
+- ✅ Test verification (Pattern 3 routing confirmed)
+- ✅ MIR PHI generation verified
+
+**Out of Scope (Phase 213)**:
+Pattern 3 lowerer (`lower_loop_with_if_phi_pattern`) is currently a **test-only PoC implementation** with hardcoded conditions and updates. AST-based generalization for if-sum patterns is handled in Phase 213.
+
+**Next**: Phase 213 will generalize Pattern 3 lowerer to read actual AST conditions and update expressions dynamically.
+
 **Phase 212.5: COMPLETE ✅**