🚀 Break/Continue/Try-Catch構文のサポート追加とMIRループ制御強化

## 主な変更点

### 🎯 MIRループ制御の実装（根治対応）
- src/mir/loop_builder.rs: Break/Continue対応のループコンテキスト管理
  - ループのbreak/continueターゲットブロック追跡
  - ネストループの適切な処理
- src/mir/builder.rs: Break/Continue文のMIR生成実装
- src/tokenizer.rs: Break/Continue/Tryトークン認識追加

### 📝 セルフホストパーサーの拡張
- apps/selfhost-compiler/boxes/parser_box.nyash:
  - Stage-3: break/continue構文受理（no-op実装）
  - Stage-3: try-catch-finally構文受理（構文解析のみ）
  - エラー処理構文の将来対応準備

### 📚 ドキュメント更新
- 論文K（爆速事件簿）: 45事例に更新（4件追加）
  - PyVM迂回路の混乱事件
  - Break/Continue無限ループ事件
  - EXE-first戦略の再発見
- 論文I（開発秘話）: Day 38の重要決定追加

### 🧪 テストケース追加
- apps/tests/: ループ制御とPHIのテストケース
  - nested_loop_inner_break_isolated.nyash
  - nested_loop_inner_continue_isolated.nyash
  - loop_phi_one_sided.nyash
  - shortcircuit関連テスト

## 技術的詳細
- Break/ContinueをMIRレベルで適切に処理
- 無限ループ問題（CPU 99.9%暴走）の根本解決
- 将来の例外処理機能への準備

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

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

tests/json_v0/arith.json

@@ -0,0 +1,8 @@
+{"version":0,"kind":"Program","body":[
+  {"type":"Return","expr":{
+    "type":"Binary","op":"+",
+    "lhs":{"type":"Int","value":1},
+    "rhs":{"type":"Binary","op":"*","lhs":{"type":"Int","value":2},"rhs":{"type":"Int","value":3}}
+  }}
+]}
+

tests/json_v0/if_then_else.json

@@ -0,0 +1,9 @@
+{"version":0,"kind":"Program","body":[
+  {"type":"Local","name":"x","expr":{"type":"Int","value":1}},
+  {"type":"If","cond":{"type":"Compare","op":"<","lhs":{"type":"Int","value":1},"rhs":{"type":"Int","value":2}},
+    "then":[{"type":"Local","name":"x","expr":{"type":"Int","value":10}}],
+    "else":[{"type":"Local","name":"x","expr":{"type":"Int","value":20}}]
+  },
+  {"type":"Return","expr":{"type":"Var","name":"x"}}
+]}
+

tests/json_v0/logical_nested.json

@@ -0,0 +1,11 @@
+{"version":0,"kind":"Program","body":[
+  {"type":"Return","expr":{
+    "type":"Logical","op":"&&",
+    "lhs":{"type":"Bool","value":true},
+    "rhs":{"type":"Logical","op":"||",
+      "lhs":{"type":"Bool","value":false},
+      "rhs":{"type":"Compare","op":"<","lhs":{"type":"Int","value":1},"rhs":{"type":"Int","value":2}}
+    }
+  }}
+]}
+

tests/json_v0/logical_shortcircuit_and.json

@@ -0,0 +1,10 @@
+{"version":0,"kind":"Program","body":[
+  {"type":"Local","name":"a","expr":{"type":"New","class":"ArrayBox","args":[]}},
+  {"type":"Local","name":"f","expr":{"type":"Bool","value":false}},
+  {"type":"Expr","expr":{"type":"Logical","op":"&&",
+    "lhs":{"type":"Var","name":"f"},
+    "rhs":{"type":"Method","recv":{"type":"Var","name":"a"},"method":"push","args":[{"type":"Int","value":1}]}
+  }},
+  {"type":"Return","expr":{"type":"Method","recv":{"type":"Var","name":"a"},"method":"size","args":[]}}
+]}
+

tests/json_v0/logical_shortcircuit_or.json

@@ -0,0 +1,10 @@
+{"version":0,"kind":"Program","body":[
+  {"type":"Local","name":"a","expr":{"type":"New","class":"ArrayBox","args":[]}},
+  {"type":"Local","name":"t","expr":{"type":"Bool","value":true}},
+  {"type":"Expr","expr":{"type":"Logical","op":"||",
+    "lhs":{"type":"Var","name":"t"},
+    "rhs":{"type":"Method","recv":{"type":"Var","name":"a"},"method":"push","args":[{"type":"Int","value":1}]}
+  }},
+  {"type":"Return","expr":{"type":"Method","recv":{"type":"Var","name":"a"},"method":"size","args":[]}}
+]}
+

tests/json_v0/method_string_length.json

@@ -0,0 +1,4 @@
+{"version":0,"kind":"Program","body":[
+  {"type":"Return","expr":{"type":"Method","recv":{"type":"Str","value":"abc"},"method":"length","args":[]}}
+]}
+

tests/json_v0/string_chain.json

@@ -0,0 +1,10 @@
+{"version":0,"kind":"Program","body":[
+  {"type":"Return","expr":{
+    "type":"Method","recv":{
+      "type":"Method","recv":{"type":"Str","value":"abcd"},
+      "method":"substring","args":[{"type":"Int","value":1},{"type":"Int","value":3}]
+    },
+    "method":"length","args":[]
+  }}
+]}
+

tests/json_v0/while_sum.json

@@ -0,0 +1,12 @@
+{"version":0,"kind":"Program","body":[
+  {"type":"Local","name":"i","expr":{"type":"Int","value":0}},
+  {"type":"Local","name":"s","expr":{"type":"Int","value":0}},
+  {"type":"Loop","cond":{"type":"Compare","op":"<","lhs":{"type":"Var","name":"i"},"rhs":{"type":"Int","value":3}},
+    "body":[
+      {"type":"Local","name":"s","expr":{"type":"Binary","op":"+","lhs":{"type":"Var","name":"s"},"rhs":{"type":"Int","value":1}}},
+      {"type":"Local","name":"i","expr":{"type":"Binary","op":"+","lhs":{"type":"Var","name":"i"},"rhs":{"type":"Int","value":1}}}
+    ]
+  },
+  {"type":"Return","expr":{"type":"Var","name":"s"}}
+]}
+