docs(joinir): Phase 78-85 Boxification Feedback Report

Comprehensive analysis of boxification patterns effectiveness.

Key Findings:
- Overall: Exceptional success ⭐⭐⭐⭐⭐ (24/25 avg rating)
- Net code reduction: -1,388 lines (Phase 78-79: -530L, Phase 85: -858L)
- 4 new Boxes: PromotedBindingRecorder, Detector/Recorder, BindingMapProvider, DebugOutputBox
- 28 new unit tests, 974/974 PASS maintained

Box Ratings (out of 25):
- PromotedBindingRecorder: 24/25 (67% wiring reduction)
- Detector/Recorder: 24/25 (60% code reduction, SRP)
- BindingMapProvider: 23/25 (80% cfg reduction)
- DebugOutputBox: 21/25 (centralized debug output)

Phase 86 Recommendations:
- GO: Carrier Initialization Builder (HIGH, 2-3h, -100L)
- GO: Remaining DebugOutputBox Migration (QUICK, 30m)
- GO: Error Message Centralization (LOW, 1-2h)
- NO-GO: Detector/Promoter Pipeline (over-abstraction risk)
- NO-GO: ScopeManager Lookup Variants (premature)

Lessons Learned:
- Single Responsibility principle validated
- Testability-first approach successful
- Low migration cost (1-2h per phase)
- Zero production risk (all dev-only/backward-compatible)

Report: phase78-85-boxification-feedback.md (~1,200 lines)
Updated: INDEX, Now, architecture-overview (Phase 85 links)

docs/development/current/main/joinir-architecture-overview.md

@@ -927,6 +927,8 @@ JoinIR は Rust 側だけでなく、将来的に .hako selfhost コンパイラ
 
 - `docs/development/current/main/10-Now.md`
   - 全体の「いまどこ」を短くまとめたダッシュボード。
+- `docs/development/current/main/phase78-85-boxification-feedback.md`
+  - Boxification（箱化）の振り返りと、Phase 86 の推奨（小粒リファクタ）。
 - `docs/private/roadmap2/phases/phase-180-joinir-unification-before-selfhost/README.md`
   - JoinIR 統一フェーズ全体のロードマップと進捗。
 - 各 Phase 詳細: