chore: Remove unused imports in normalized_shadow modules

Cleaned up unused imports after Phase 143 execution fix (5e662eaaf).

**Priority files (Phase 143)**:
- if_as_last_join_k.rs: removed ValueId, BTreeMap
- loop_true_break_once.rs: added #[cfg(test)] for test-only imports
- post_if_post_k.rs: removed ValueId, BTreeMap
- normalized_helpers.rs: added #[cfg(test)] for Span

**Additional cleanup**:
- contract_checks.rs: removed BasicBlockId
- joinir/mod.rs: removed Info struct re-exports (functions kept)
- patterns/mod.rs: removed Info struct re-exports (functions kept)
- ast_feature_extractor.rs: removed EscapeSkipPatternInfo
- plan_box.rs: added #[cfg(test)] for PlanKind

**Verification**:
- 0 unused import warnings (was 20+)
- All 69 normalized_shadow tests pass
- Clean build with --release

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

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

docs/development/current/main/30-Backlog.md

@@ -16,6 +16,13 @@ Related:
     - out-of-scope は `Ok(None)` でフォールバック（既定挙動不変）
     - effects の順序付けは SSOT で固定してから解禁（by-name 増殖禁止）
 
+- **Phase 144-anf（planned）: impure 式導入の順序固定（ANF）**
+  - ねらい: `x + f(y)` 等の “pure + impure 混在” で評価順が仕様になる前に、ANF で順序固定を SSOT 化する
+  - 入口: `docs/development/current/main/phases/phase-144-anf/INSTRUCTIONS.md`
+  - 受け入れ条件:
+    - impure を lowering できない場合は `Ok(None)` でフォールバック（既定挙動不変）
+    - dev/strict では「順序固定の欠落」を Fail-Fast（診断に順序ログを含める）
+
 - **Phase 143-loopvocab R0（planned）: Contract SSOT 抽出（refactor P0 → modular components）**
   - 目的: loop_true_if_break_continue.rs を「検出/契約/変換」に分割し、P1/P2 での if分岐増殖を防ぐ
   - 実装: