feat(phase-91): Step 2-A完了 - AST recognizer & re-export chain

## Step 2-A: AST Recognizer (detect_escape_skip_pattern)
- 追加ファイル: src/mir/builder/control_flow/joinir/patterns/ast_feature_extractor.rs
  - EscapeSkipPatternInfo 構造体定義
  - detect_escape_skip_pattern() メイン関数 (MVP実装)
  - Helper関数: find_break_in_if, find_escape_in_if, find_normal_increment等

## Step 2-B: Re-export Chain (SSOT準備)
- 5ファイルで re-export を追加:
  1. src/mir/builder/control_flow/joinir/patterns/mod.rs
  2. src/mir/builder/control_flow/joinir/mod.rs
  3. src/mir/builder/control_flow/mod.rs
  4. src/mir/builder.rs
  5. src/mir/mod.rs
  6. src/mir/loop_canonicalizer/pattern_recognizer.rs

## Pattern Recognizer Wrapper
- try_extract_escape_skip_pattern() を pattern_recognizer.rs に追加
- 既存パターン（skip_whitespace等）に倣う設計

## Phase 91 MVP Design
- Quote/escape char は期待値（"と\）にハードコード（Phase 91 MVP）
- Normal delta は常に1を期待
- Escape delta は AST から抽出

## Test Results
✅ cargo build --release: 成功
✅ cargo test --release --lib: 1061/1061 PASS
- 退行なし

## 次: Step 2-B本体 (Canonicalizer統合)
- canonicalizer.rs に detect_escape_skip_pattern() 統合
- LoopSkeleton & RoutingDecision を構築
- Pattern2Break に寄せる

🤖 Generated with Claude Code

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

src/mir/builder.rs

@@ -38,6 +38,8 @@ pub(crate) use control_flow::{detect_continue_pattern, ContinuePatternInfo};
 // Phase 143-P0: Re-export parse_number pattern detection for loop_canonicalizer
 pub(crate) use control_flow::{detect_parse_number_pattern, ParseNumberInfo};
 pub(crate) use control_flow::{detect_parse_string_pattern, ParseStringInfo};
+// Phase 91 P5b: Re-export escape skip pattern detection for loop_canonicalizer
+pub(crate) use control_flow::{detect_escape_skip_pattern, EscapeSkipPatternInfo};
 mod exprs_lambda; // lambda lowering
 mod exprs_peek; // peek expression
 mod exprs_qmark; // ?-propagate