📚 Phase 15 - セルフホスティング戦略の明確化とEXE-first実装

## 主な変更点

### 🎯 戦略の転換と明確化
- PyVMを開発ツールとして位置づけ（本番経路ではない）
- EXE-first戦略を明確に優先（build_compiler_exe.sh実装済み）
- Phase順序の整理: 15.2(LLVM)→15.3(コンパイラ)→15.4(VM)

### 🚀 セルフホスティング基盤の実装
- apps/selfhost-compiler/にNyashコンパイラMVP実装
  - compiler.nyash: メインエントリー（位置引数対応）
  - boxes/: parser_box, emitter_box, debug_box分離
- tools/build_compiler_exe.sh: ネイティブEXEビルド＋dist配布
- Python MVPパーサーStage-2完成（local/if/loop/call/method/new）

### 📝 ドキュメント整備
- Phase 15 README/ROADMAP更新（Self-Hosting優先明記）
- docs/guides/exe-first-wsl.md: WSLクイックスタート追加
- docs/private/papers/: 論文G～L、爆速事件簿41事例収録

### 🔧 技術的改善
- JSON v0 Bridge: If/Loop PHI生成実装（ChatGPT協力）
- PyVM/llvmliteパリティ検証スイート追加
- using/namespace機能（gated実装、Phase 15では非解決）

## 次のステップ
1. パーサー無限ループ修正（未実装関数の実装）
2. EXEビルドとセルフホスティング実証
3. c0→c1→c1'ブートストラップループ確立

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

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

docs/reference/language/using.md

@@ -0,0 +1,45 @@
+# using — Imports and Namespaces (Phase 15)
+
+Status: Accepted (Runner‑side resolution). Selfhost parser accepts using as no‑op and attaches `meta.usings` for future use.
+
+Policy
+- Accept `using` lines at the top of the file to declare module namespaces or file imports.
+- Resolution is performed by the Rust Runner when `NYASH_ENABLE_USING=1`.
+  - Runner strips `using` lines from the source before parsing/execution.
+  - Registers modules into an internal registry for path/namespace hints.
+- Selfhost compiler (Ny→JSON v0) collects using lines and emits `meta.usings` when present. The bridge currently ignores this meta field.
+
+Syntax
+- Namespace: `using core.std` or `using core.std as Std`
+- File path: `using "apps/examples/string_p0.nyash" as Strings`
+- Relative path is allowed; absolute paths are discouraged.
+
+Style
+- Place all `using` lines at the top of the file, before any code.
+- One using per line; avoid trailing semicolons. Newline separation is preferred.
+- Order: sort alphabetically by target. Group namespaces before file paths.
+- Prefer an explicit alias (`as ...`) when the target is long. Suggested alias style is `PascalCase` (e.g., `Std`, `Json`, `UI`).
+
+Examples
+```nyash
+using core.std as Std
+using "apps/examples/string_p0.nyash" as Strings
+
+static box Main {
+  main(args) {
+    local console = new ConsoleBox()
+    console.println("hello")
+    return 0
+  }
+}
+```
+
+Runner Configuration
+- Enable using pre‑processing: `NYASH_ENABLE_USING=1`
+- Selfhost pipeline keeps child stdout quiet and extracts JSON only: `NYASH_JSON_ONLY=1` (set by Runner automatically for child)
+- Selfhost emits `meta.usings` automatically when present; no additional flags required.
+
+Notes
+- Phase 15 keeps resolution in the Runner to minimize parser complexity. Future phases may leverage `meta.usings` for compiler decisions.
+- Unknown fields in the top‑level JSON (like `meta`) are ignored by the current bridge.
+