refactor(mir): Phase 140-P4-B - pattern_recognizer を SSOT 化（71 行削減）

- try_extract_skip_whitespace_pattern を ast_feature_extractor 呼び出しに変更
- 重複コード 100+ 行削減（250 → 179 行）
- crate-wide re-export chain 確立（ast_feature_extractor → patterns → joinir → control_flow → builder → mir）
- 全テスト PASS（14 tests）
- フォーマット適用

Phase 140-P4-A/P4-B 完了：SSOT 化成功

src/mir/builder.rs

@@ -28,8 +28,11 @@ mod exprs_call;
 mod metadata_context; // Phase 136 follow-up (Step 6/7): MetadataContext extraction
 mod method_call_handlers;
 mod variable_context; // Phase 136 follow-up (Step 5/7): VariableContext extraction // Method call handler separation (Phase 3) // call(expr)
-                                                                                    // include lowering removed (using is handled in runner)
+                      // include lowering removed (using is handled in runner)
 mod control_flow; // thin wrappers to centralize control-flow entrypoints
+
+// Phase 140-P4-A: Re-export for loop_canonicalizer SSOT (crate-wide visibility)
+pub(crate) use control_flow::{detect_skip_whitespace_pattern, SkipWhitespaceInfo};
 mod exprs_lambda; // lambda lowering
 mod exprs_peek; // peek expression
 mod exprs_qmark; // ?-propagate