feat: using system完全実装＋旧スモークテストアーカイブ完了

✅ using nyashstd完全動作（ChatGPT実装）
- builtin:nyashstd自動解決
- 環境変数不要でデフォルト有効
- console.log等の基本機能完備

✅ Fixture plugin追加（テスト用最小構成）
✅ v2スモークテスト構造への移行
✅ 旧tools/test/smoke/削除（100+ファイル）

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>

src/using/mod.rs

@@ -0,0 +1,19 @@
+/*!\
+ Using system — resolution scaffolding (Phase 15 skeleton)\
+\
+ Centralizes name/path resolution for `using` statements.\
+ This initial cut only reads nyash.toml to populate:\
+  - [using.paths]  → search roots for source lookups\
+  - [modules]      → logical name → file path mapping\
+  - [aliases]      → convenience alias mapping (optional)\
+\
+ The goal is to keep runner/pipeline lean by delegating nyash.toml parsing here,\
+ without changing default behavior. Future work will add: file/DLL specs, policies,\
+ and plugin metadata fusion (nyash_box.toml / embedded BID).\
+*/
+
+pub mod resolver;
+pub mod spec;
+pub mod policy;
+pub mod errors;
+pub mod simple_registry;