docs: Phase 100 P2.1 - LLVM EXE parity for mutable accumulator

- Update phases/phase-100/README.md with LLVM EXE smoke note
- Update 10-Now.md with P2.1 short report

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

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

@@ -1,5 +1,13 @@
 # Self Current Task — Now (main)
 
+## 2025-12-17：Phase 100 P2 完了 ✅
+
+**Phase 100 P2: Mutable Accumulator Captures**
+- Mutable accumulator pattern (`out = out + ch`) を Pattern2 carrier で対応
+- ScopeManager 委譲により read-only check を回避
+- Numeric output validation (count=3) で fixture 固定
+- VM/LLVM EXE parity 完了（smoke 追加）
+
 ## 2025-12-17：Phase 100 P1 完了 ✅
 
 **Phase 100 P1: Pinned Local Captures**