feat(phase285): Complete weak reference implementation (VM + LLVM harness)

Phase 285LLVM-1.1 to 1.4 + weak reference infrastructure:

**LLVM Harness** (Phase 285LLVM-1.x):
- 285LLVM-1.1: User Box registration & debug output
- 285LLVM-1.2: WeakRef basic operations (identity deferred)
- 285LLVM-1.3: InstanceBox field access (getField/setField)
- 285LLVM-1.4: print Handle resolution (type tag propagation)

**VM Runtime** (nyash_kernel):
- FFI functions: nyrt_weak_new, nyrt_weak_to_strong, nyrt_weak_drop
  (crates/nyash_kernel/src/lib.rs: +209 lines)
- WeakRef plugin invoke support
  (crates/nyash_kernel/src/plugin/invoke.rs: +250 lines)
- weak_handles.rs: WeakRef handle registry (NEW)

**LLVM Python Backend**:
- WeakRef instruction lowering (weak.py: NEW)
- Entry point integration (entry.py: +93 lines)
- Instruction lowering (instruction_lower.py: +13 lines)
- LLVM harness runner script (tools/run_llvm_harness.sh: NEW)

**MIR & Runtime**:
- WeakRef emission & validation
- MIR JSON export for weak instructions
- Environment variable support (NYASH_WEAK_*, HAKO_WEAK_*)

**Documentation**:
- CLAUDE.md: Phase 285 completion notes
- LANGUAGE_REFERENCE_2025.md: Weak reference syntax
- 10-Now.md & 30-Backlog.md: Phase 285 status updates

Total: +864 lines, 24 files changed

SSOT: docs/reference/language/lifecycle.md
Related: Phase 285W-Syntax-0, Phase 285W-Syntax-0.1

docs/development/current/main/10-Now.md

@@ -9,7 +9,25 @@
   - 次: Phase 285（design-first）Box lifecycle SSOT（`docs/development/current/main/phases/phase-285/README.md`）
   - 次の次: Phase 286（design-first）JoinIR line absorption（`docs/development/current/main/phases/phase-286/README.md`）
 
-## Recently Completed (2025-12-23)
+## Recently Completed
+
+### 2025-12-24: Phase 285LLVM-1.3（LLVM InstanceBox Field Access）
+
+- ✅ **Phase 285LLVM-1.3完了**: InstanceBox field access (getField/setField) implementation
+  - 詳細: `docs/development/current/main/phases/phase-285/phase-285llvm-1.3-verification-report.md`
+  - 実装: `crates/nyash_kernel/src/plugin/invoke.rs` (~170 lines)
+  - 達成内容:
+    - ✅ getField/setField handlers 実装完了（SSOT `fields_ng` 直接アクセス）
+    - ✅ Fail-Fast error logging 実装（`[llvm/invoke/{get,set}Field]` tags）
+    - ✅ Raw i64 fallback 対応（LLVM backend 特有の挙動）
+    - ✅ Handle resolution 動作確認（handle 4 → IntegerBox(42)）
+  - 検証結果:
+    - ✅ setField: Integer(42) を正しく保存
+    - ✅ getField: Integer(42) を正しく取得、handle 返却
+    - ⚠️ print issue: handle 解決問題により VM/LLVM parity blocked（Phase 285LLVM-1.4で対応）
+  - 次フェーズ: Phase 285LLVM-1.4 (print Handle Resolution, 推定2-4時間)
+
+### 2025-12-23
 
 - Phase 283（bugfix）: JoinIR if-condition remap fix: `docs/development/current/main/phases/phase-283/README.md`
 - Phase 282（Router shrinkage + extraction-based migration + extractor refactor P0–P9a）: `docs/development/current/main/phases/phase-282/README.md`