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**

docs/development/current/main/phases/phase-100/README.md

@@ -109,3 +109,5 @@ print(out.length())   # Output: 2
 - **P2-2**: Pattern2 wiring (ScopeManager delegates read-only check)
 - **P2-3**: Lowering (carrier update emission)
 - **P2-4**: Integration test (fixture + smoke, length-based validation)
+
+**LLVM EXE parity**: P2 accumulator を LLVM EXE smoke でも固定（phase100_mutable_accumulator_llvm_exe.sh）