Add Rust ownership fusion theory and fix smoke test paths

🦀📦 Added Rust×Nyash ownership fusion design (Phase 17+ candidate)
- Comprehensive ownership integration proposal with tags + borrowing tokens
- 3-tier safety levels (Safe/Unsafe/FFI) with opt-in adoption
- Complete link integration across roadmap and docs

🔧 Fixed smoke test path resolution
- Corrected ROOT_DIR calculation in selfhost smoke tests
- Updated scopebox_identity_smoke.sh, loopform_identity_smoke.sh, selfhost_runner_smoke.sh

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

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

docs/development/roadmap/phases/00_MASTER_ROADMAP.md

@@ -32,6 +32,7 @@ Purpose: Claude×Copilot×ChatGPT×Gemini×Codex協調開発の総合ロード
 | 15 | 🌟実現可能 | セルフホスティング（C実装ABI経由） | [phase-15/](phase-15/) |
 | 16 | 🔄進行中 | マクロ革命（正規化＋テストランナー） | [phase-16-macro-revolution/](../phase-16-macro-revolution/) |
 | 17 | 🧪計画中 | LoopForm Self‑Hosting＋Mini‑VM | [phase-17-loopform-selfhost/](../phase-17-loopform-selfhost/) |
+| 17+ | 💡候補 | Rust所有権統合（オプショナル） | [rust-ownership-fusion](../../private/ideas/new-features/2025-09-22-rust-ownership-fusion.md) |
 
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