feat(plugin): Fix plugin BoxRef return and Box argument support

- Fixed deadlock in FileBox plugin copyFrom implementation (single lock)
- Added TLV Handle (tag=8) parsing in calls.rs for returned BoxRefs
- Improved plugin loader with config path consistency and detailed logging
- Fixed loader routing for proper Handle type_id/fini_method_id resolution
- Added detailed logging for TLV encoding/decoding in plugin_loader_v2

Test docs/examples/plugin_boxref_return.nyash now works correctly:
- cloneSelf() returns FileBox Handle properly
- copyFrom(Box) accepts plugin Box arguments
- Both FileBox instances close and fini correctly

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

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

docs/development/proposals/nyir/spec.md

@@ -0,0 +1,126 @@
+# NyIR v1 Specification (Draft Skeleton)
+
+Purpose
+- Define NyIR (public intermediate representation) as the portable contract for all frontends/backends.
+- Freeze the 25-instruction set, effects, ownership forest, weak semantics, and bus contract.
+
+Status
+- Version: nyir1.0 (draft)
+- Change policy: backward-compatible extensions via feature bits; no undefined behavior.
+
+1. Instruction Set (26) — Semantic Summary
+- Tier-0: Const, BinOp, Compare, Branch, Jump, Phi, Call, Return
+- Tier-1: NewBox, BoxFieldLoad, BoxFieldStore, BoxCall, ExternCall, Safepoint, RefGet, RefSet, WeakNew, WeakLoad, WeakCheck, Send, Recv
+- Tier-2: TailCall, Adopt, Release, MemCopy, AtomicFence
+
+For each instruction (to be filled):
+- Semantics: preconditions, side-effects, failure behavior
+- Effects: pure/mut/io/control
+- Verification: structural/formal checks
+- Example: minimal snippet
+
+2. Effects Model
+- pure: no observable side effects; can reorder with pure
+- mut: mutates owned state; preserve order per resource
+- io: interacts with outside world; preserve program order
+- control: affects control flow/terminators
+
+3. Ownership Forest
+- Strong edges form a forest (strong in-degree ≤ 1).
+- No strong cycles.
+- Weak edges do not propagate ownership.
+- Adopt/Release rules; Safepoint and split-fini notes.
+
+4. Weak Semantics
+- Representation: {ptr, generation}
+- WeakLoad: returns null if generation mismatch
+- WeakCheck: returns false if invalid
+- O(1) on-access validation
+
+5. Bus Contract
+- Local: in-order delivery
+- Remote: at-least-once (or selectable); specify ordering/dup policy
+
+6. Formats
+- Text .nyir: human-readable; module header, features, const pool, functions (blocks, instrs)
+- Binary .nybc: sectioned; header, features, const pool, functions, metadata; varint encodings
+- Feature bits and extension sections for evolution
+
+7. Verification
+- Program well-formedness: reachability, termination, dominance
+- Phi input consistency
+- Effects ordering constraints
+- Ownership forest & weak/generation rules
+- Bus safety checks
+
+8. External Calls (Core)
+- ExternCall: Interface to external libraries as Everything is Box principle
+- Format: ExternCall { dst, iface_name, method_name, args }
+- Effect annotation required (pure/mut/io/control)
+- BID (Box Interface Definition) provides external API contracts
+
+9. Mapping Guidelines
+- WASM: imports, memory rules, (ptr,len) strings
+- VM: function table mapping
+- LLVM: declare signatures; effect to attributes (readonly/readnone, etc.)
+
+10. Golden/Differential Testing
+- Golden .nyir corpus; cross-backend consistency (interp/vm/wasm/llvm)
+
+11. Versioning & Compatibility
+- nyir{major.minor}; feature negotiation and safe fallback
+
+12. Glossary
+- Box, Effect, Ownership forest, Weak, Safepoint, Bus, Feature bit
+
+Appendix
+- Minimal examples (to be added)
+- Rationale notes
+
+------------------------------------------------------------
+NyIR-Ext（拡張セット）
+------------------------------------------------------------
+
+目的
+- NyIR Core（26命令）は基本セマンティクス凍結。外部世界接続（ExternCall）を含む基本機能確立。
+- 拡張は言語固有機能に限定：「例外」「軽量並行/非同期」「アトミック」の3領域を段階追加。
+- Core機能: すべての言語で必要な基本セマンティクス（制御フロー・Box操作・外部呼び出し）
+- Extension機能: 特定言語でのみ必要な高級機能（例外処理・並行処理・アトミック操作）
+
+Ext-1: 例外/アンワインド（exceptions）
+- 命令（案）：
+  - Throw(value)
+  - TryBegin
+  - TryEnd(handlers=[type:block])
+- 効果: control（脱出）。mut/io と混在する場合は当該効果も従属。
+- 検証: Try の整合（入れ子/終端）、未捕捉 Throw のスコープ明示、no-throw 関数属性の尊重。
+- バックエンド指針:
+  - LLVM: 言語EH or setjmp/longjmp 系へ lower
+  - WASM: v0は例外未使用なら「エラー戻り値」へ降格（no-exception モード）
+
+Ext-2: 軽量並行/非同期（concurrency）
+- 命令（案）：
+  - Spawn(fn, args...)
+  - Join(handle)
+  - Await(task|event)  // または Wait
+- 効果: io（スケジューラ相互作用）＋ control（待機・解除）。
+- 検証: Join/Spawn のライフサイクル均衡、待機の整合（任意でデッドロック静的ヒント）。
+- バックエンド指針:
+  - LLVM: pthread/std::thread/独自ランタイム
+  - WASM: スレッド未使用ならランループ/Promise/MessageChannel 等で近似
+
+Ext-3: アトミック（atomics）
+- 命令（案）：
+  - AtomicRmw(op, addr, val, ordering=seq_cst)
+  - CAS(addr, expect, replace, ordering=seq_cst)
+- 既存の AtomicFence は維持。
+- 効果: mut（アトミック副作用）。必要に応じて atomic/volatile フラグを effect/属性で付与。
+- バックエンド指針:
+  - LLVM: `atomicrmw`, `cmpxchg`
+  - WASM: Threads 提案が前提。未サポート環境では未実装 or 疑似ロック（デモ用途）
+
+備考
+- 可変引数は slice 表現で代替（IR 追加不要）。
+- クロージャ捕捉は Box + env フィールド + BoxCall で表現（IR 追加不要）。
+- 動的言語（辞書/配列/プロトタイプ）は標準Box（std）で受ける（IR 追加不要）。
+- 関数属性に「エラー戻り値モード/no-exception」などのメタを付与し、例外禁止環境へも対応する。