Phase 10.7 - JIT統計とイベント機能の完成

主要な実装:
- PHI(b1)統計追跡: phi_total_slots/phi_b1_slotsをJSON出力
- 関数単位統計API: JitStatsBox.perFunction()で詳細統計取得
- JITイベントシステム: compile/execute/fallback/trapをJSONL形式で記録
- Store/Load命令対応: ローカル変数を含む関数のJIT実行が可能に

新しいBox:
- JitStatsBox: JIT統計の取得
- JitConfigBox: JIT設定の管理（将来用）
- JitEventsBox: イベントのJSONL出力（将来用）
- JitPolicyBox: 実行ポリシー管理（将来用）

CLI拡張:
- --jit-exec, --jit-stats, --jit-dump等のフラグ追加
- --jit-directモードでの独立JIT実行
- NYASH_JIT_*環境変数によるきめ細かい制御

ドキュメント:
- Phase 10.7実装計画の詳細化
- Phase 10.9 (ビルトインBox JIT) の計画追加
- JIT統計JSONスキーマ v1の仕様化

ChatGPT5との共同開発により、JIT基盤が大幅に強化されました。
次はPhase 10.9でビルトインBoxのJIT対応を進め、
Python統合（Phase 10.1）への道を開きます。

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

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

docs/reference/jit/jit_stats_json_v1.md

@@ -0,0 +1,76 @@
+JIT Stats JSON Schema — Version 1
+=================================
+
+This document describes the fields emitted in the JIT statistics JSON outputs (version=1).
+
+Sources
+- Unified JIT stats (VM-side): printed when `NYASH_JIT_STATS_JSON=1` (or CLI equivalent)
+- Box API: `new JitStatsBox().toJson()` returns a compact JSON, `summary()` returns a pretty JSON summary (via VM dispatch)
+
+Version
+- `version`: number — Schema version (currently `1`)
+
+Unified JIT Stats (JSON)
+- `version`: number — Schema version (1)
+- `sites`: number — Number of JIT call sites observed
+- `compiled`: number — Count of functions compiled by the JIT
+- `hits`: number — Sum of entries across all functions (hotness hits)
+- `exec_ok`: number — Count of successful JIT executions
+- `trap`: number — Count of JIT executions that trapped and fell back to VM
+- `fallback_rate`: number — Ratio `trap / (exec_ok + trap)` (0 when denominator is 0)
+- `handles`: number — Current number of live JIT handles in the registry
+- `abi_mode`: string — `"i64_bool"` or `"b1_bool"` (when toolchain supports b1)
+- `abi_b1_enabled`: boolean — Whether b1 ABI is requested by config
+- `abi_b1_supported`: boolean — Whether current toolchain supports b1 in signatures
+- `b1_norm_count`: number — Count of b1 normalizations (e.g., i64!=0 to b1)
+- `ret_bool_hint_count`: number — Count of functions lowered with return-bool hint
+- `phi_total_slots`: number — Total PHI slots encountered (always-on, LowerCore-based)
+- `phi_b1_slots`: number — PHI slots classified as boolean (heuristics)
+- `top5`: array of objects — Top hot functions
+  - `name`: string
+  - `hits`: number
+  - `compiled`: boolean
+  - `handle`: number (0 when not compiled)
+
+Compact Box JSON — `JitStatsBox.toJson()`
+- `version`: number — Schema version (1)
+- `abi_mode`: string — Current ABI mode for booleans (see above)
+- `abi_b1_enabled`: boolean — Whether b1 ABI is requested by config
+- `abi_b1_supported`: boolean — Whether current toolchain supports b1 in signatures
+- `b1_norm_count`: number — b1 normalizations count
+- `ret_bool_hint_count`: number — return-bool hint count
+- `phi_total_slots`: number — Total PHI slots (accumulated)
+- `phi_b1_slots`: number — Boolean PHI slots (accumulated)
+
+Summary Box JSON — `JitStatsBox.summary()`
+- Pretty-printed JSON containing:
+  - All fields from `toJson()`
+  - `top5`: same structure as unified stats
+
+Notes
+- Counters reflect process-lifetime totals (reset only on process start).
+- `phi_*` counters are accumulated per LowerCore invocation (function lower), independent of dump flags.
+- `abi_mode` switches to `b1_bool` when toolchain support is detected and b1 ABI is enabled.
+
+Examples
+```
+{
+  "version": 1,
+  "sites": 1,
+  "compiled": 0,
+  "hits": 1,
+  "exec_ok": 0,
+  "trap": 0,
+  "fallback_rate": 0.0,
+  "handles": 0,
+  "abi_mode": "i64_bool",
+  "abi_b1_enabled": false,
+  "abi_b1_supported": false,
+  "b1_norm_count": 0,
+  "ret_bool_hint_count": 0,
+  "phi_total_slots": 2,
+  "phi_b1_slots": 1,
+  "top5": [ { "name": "main", "hits": 1, "compiled": false, "handle": 0 } ]
+}
+```
+