docs: Phase 136/137 - return literal and add expression documentation

Phase 136 Documentation:
- Created docs/development/current/main/phases/phase-136/README.md
- Goal: loop(true) break-once with return literal (Integer)
- Supported: return 7, loop + post + return literal
- Implementation: lower_return_value_to_vid() method
- Tests: 2 fixtures + 4 smokes
- VM/LLVM EXE parity verification commands

Phase 137 Documentation:
- Created docs/development/current/main/phases/phase-137/README.md
- Goal: loop(true) break-once with return add expression
- Supported: return x+2, return 5+3, loop+post+return add
- Implementation: Extended lower_return_value_to_vid() for BinaryOp Add
- Return Value Lowering SSOT documented (lines 29-46)
- Boxification trigger: when 2+ files need identical logic
- Tests: 3 fixtures + 6 smokes
- VM/LLVM EXE parity verification commands

10-Now.md Updates:
- Added Phase 136 entry (return literal)
- Added Phase 137 entry (return add expression)
- Implementation details and test coverage
- Links to phase READMEs

🤖 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 +1,62 @@
 # Self Current Task — Now (main)
 
+## 2025-12-18：Phase 137 完了 ✅
+
+**Phase 137: loop(true) break-once with return add expression**
+- 目的: Phase 136 を拡張し、return 時に最小 add 式をサポート
+- 仕様:
+  - `return x + 2`（variable + integer literal）→ exit code 3
+  - `return 5 + 3`（integer literal + integer literal）→ exit code 8
+  - `loop(true) { x = 1; break }; x = x + 10; return x + 2` → exit code 13
+- 実装:
+  - `src/mir/control_tree/normalized_shadow/loop_true_break_once.rs`（`lower_return_value_to_vid()` 行 638-743, BinaryOp Add at 行 673）
+  - BinaryOp Add パターン追加（LHS: Variable or Integer literal, RHS: Integer literal only）
+  - Ok(None) fallback for out-of-scope patterns（`return x + y`, `return x - 2` 等）
+- Return Value Lowering SSOT:
+  - Documentation: `loop_true_break_once.rs`（行 29-46, module-level comment）
+  - Boxification trigger: 2+ files で同一 return lowering logic が必要になった時
+- Fixtures:
+  - `phase137_loop_true_break_once_return_add_min.hako`（期待: exit code 3）
+  - `phase137_loop_true_break_once_return_add_const_min.hako`（期待: exit code 8）
+  - `phase137_loop_true_break_once_post_return_add_min.hako`（期待: exit code 13）
+- Smoke tests:
+  - VM: 3/3 PASS
+  - LLVM EXE: 3/3 PASS
+- Regression:
+  - Phase 97: 2/2 PASS（next_non_ws, json_loader_escape）
+  - Phase 131/135/136: 3/3 PASS
+- 設計判断（Approach A 採用）:
+  - 直接拡張（boxification なし）、変更スコープ小
+  - post_if_post_k.rs は未変更（責任分離）
+- 入口: `docs/development/current/main/phases/phase-137/README.md`
+
+---
+
+## 2025-12-18：Phase 136 完了 ✅
+
+**Phase 136: loop(true) break-once with return literal**
+- 目的: Phase 131-135 を拡張し、return integer literal をサポート
+- 仕様:
+  - `loop(true) { x = 1; break }; return 7` → exit code 7
+  - `loop(true) { x = 1; break }; x = x + 2; return 7` → exit code 7
+  - PHI禁止維持、dev-only、既定挙動不変
+- 実装:
+  - `src/mir/control_tree/normalized_shadow/loop_true_break_once.rs`（`lower_return_value_to_vid()` 行 638-743, Integer literal at 行 661）
+  - Integer literal パターン: Const generation（Phase 123 パターン再利用）
+  - Ok(None) fallback for out-of-scope patterns（`return "hello"`, `return 3.14` 等）
+- Fixtures:
+  - `phase136_loop_true_break_once_return_literal_min.hako`（期待: exit code 7）
+  - `phase136_loop_true_break_once_post_return_literal_min.hako`（期待: exit code 7）
+- Smoke tests:
+  - VM: 2/2 PASS
+  - LLVM EXE: 2/2 PASS
+- Regression:
+  - Phase 131: 2/2 PASS
+  - Phase 135: 2/2 PASS
+- 入口: `docs/development/current/main/phases/phase-136/README.md`
+
+---
+
 ## 2025-12-18：Phase 135 P0 完了 ✅
 
 **Phase 135 P0: Normalization Plan Suffix Detection Generalization**