feat(joinir): Phase 64-1/2 P2型ヒント実装 & 削減条件準備

Phase 64-1: P2/P3 対象関数分類完了
- P2 対象リスト作成: read_quoted_from, IfMerge Simple/Multiple
- P3 将来拡張: MethodCall戻り値型, Box コンストラクタ
- 実装戦略確立: P2から1関数ずつ段階的拡大

Phase 64-2: P2 型ヒント供給実装完了
- read_quoted.rs: ループカウンタ i (Integer), 文字列 ch (String) 型確定
- if_merge.rs: infer_type_from_mir_pattern() 追加 (Const命令から型推論)
- A/B テスト追加: test_p2_if_merge_type_hint() で型ヒント伝播検証 ✅

技術的成果:
- JoinIR MergePair の type_hint 自動推論システム完成
- Phase 63 P1実装パターンを P2 に拡大適用
- 次ステップ: Phase 64-3 lifecycle.rs で P2 hint経路統合

修正ファイル:
- phase-63-joinir-type-info/README.md: Phase 64-1/2 セクション追加
- read_quoted.rs: MergePair 型ヒント追加 (Integer/String)
- if_merge.rs: infer_type_from_mir_pattern() + 型ヒント推論
- mir_joinir_if_select.rs: test_p2_if_merge_type_hint() 追加

🎯 削除条件 4/5 維持 (P1完了), Phase 64-3で P2拡大へ

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

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

src/grammar/generated.rs

@@ -36,15 +36,37 @@ pub static OPERATORS_DIV_RULES: &[(&str, &str, &str, &str)] = &[
 ];
 pub fn lookup_keyword(word: &str) -> Option<&'static str> {
     for (k, t) in KEYWORDS {
-        if *k == word {
-            return Some(*t);
-        }
+        if *k == word { return Some(*t); }
     }
     None
 }
 
 pub static SYNTAX_ALLOWED_STATEMENTS: &[&str] = &[
-    "box", "global", "function", "static", "if", "loop", "break", "return", "print", "nowait",
-    "include", "local", "outbox", "try", "throw", "using", "from",
+    "box",
+    "global",
+    "function",
+    "static",
+    "if",
+    "loop",
+    "break",
+    "return",
+    "print",
+    "nowait",
+    "include",
+    "local",
+    "outbox",
+    "try",
+    "throw",
+    "using",
+    "from",
 ];
-pub static SYNTAX_ALLOWED_BINOPS: &[&str] = &["add", "sub", "mul", "div", "and", "or", "eq", "ne"];
+pub static SYNTAX_ALLOWED_BINOPS: &[&str] = &[
+    "add",
+    "sub",
+    "mul",
+    "div",
+    "and",
+    "or",
+    "eq",
+    "ne",
+];