feat(phase143/r0): Contract SSOT extraction - loop-if-exit pattern refactoring

Phase 143 R0: Refactor P0 to prevent if-branch explosion in P1/P2

**Key Changes**:
- New: loop_if_exit_contract.rs (LoopIfExitShape, LoopIfExitThen, OutOfScopeReason)
- Contract SSOT for pattern shape detection and exit action discrimination
- Separated unit tests to tests/phase143_loop_if_exit_contract.rs (8 tests)
- Removed embedded tests from implementation file
- Updated module declarations for contract and test modules

**Benefits**:
- Enum-driven pattern discrimination (no if-branch explosion)
- P1 extension: Add Continue via 1 enum variant + 1 match arm
- P2 extension: Add else via contract fields (linear growth, not exponential)
- Improved maintainability and code discoverability

**Verification**:
- cargo check: ✅ 0 errors
- Unit tests: ✅ 8/8 passed
- Documentation: ✅ Updated 10-Now.md and 30-Backlog.md

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

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

docs/development/current/main/10-Now.md

@@ -3,9 +3,35 @@
 ## Next (planned)
 
 - Phase 141 P2+: Call/MethodCall 対応（effects + typing を分離して段階投入）
-- Phase 143-loopvocab: StepTree の語彙拡張（loop 内 if/break/continue を「新パターン追加」ではなく「語彙追加」で吸収）
+- Phase 143-loopvocab R0+: StepTree の語彙拡張（loop 内 if/break/continue を「新パターン追加」ではなく「語彙追加」で吸収）
+  - R0: Contract SSOT 抽出（pattern shape と exit action の分離）
+  - P1: continue 支援を追加
+  - P2: else/対称branch 対応
 - 詳細: `docs/development/current/main/30-Backlog.md`
 
+## 2025-12-19：Phase 143-loopvocab P0 完了 ✅
+
+**Phase 143-loopvocab P0: Conditional Break Vocabulary Extension**
+- 目的: `loop(true) { if(cond_pure) break }` パターンを Normalized shadow で実装（Phase 131 の条件付き拡張）
+- 仕様:
+  - Loop条件: `true` リテラルのみ
+  - ループ本体: 単一 if statement（else なし）
+  - If then: `break` のみ（no continue, no nested if）
+  - 条件: pure expression のみ（変数/リテラル/算術/比較、Method call なし）
+  - Out-of-scope は `Ok(None)` で graceful fallback
+- 実装 SSOT:
+  - `src/mir/control_tree/normalized_shadow/loop_true_if_break_continue.rs`
+  - 6-function JoinModule（main → loop_step → loop_cond_check → Jump/Call → k_exit → Ret）
+  - Jump: if true → k_exit, if false → fall through to Call(loop_step)
+- Fixtures:
+  - `apps/tests/phase143_loop_true_if_break_min.hako`（expected exit code 1）
+- Smoke tests:
+  - VM: `tools/smokes/v2/profiles/integration/apps/phase143_loop_true_if_break_vm.sh` ✅ PASS
+  - LLVM EXE: `tools/smokes/v2/profiles/integration/apps/phase143_loop_true_if_break_llvm_exe.sh` ✅ PASS
+- Regression: Phase 131-142 green（no regressions）
+- 統計: +400 lines（loop_true_if_break_continue.rs）, 0 change to existing code
+- 入口: `docs/development/current/main/phases/phase-143-loopvocab/README.md`
+
 ## 2025-12-19：Phase 142-loopstmt P0 完了 ✅
 
 **Phase 142-loopstmt P0: Statement-Level Loop Normalization**