refactor(llvm): Phase 131-12-P2 - block_end_values SSOT 化（WIP）

## 実装内容
- get_end_values() API 追加
- _value_at_end_i64() を snapshot-only に変更
- def_blocks 即時更新
- PHI incoming を snapshot から取得

## 発見された問題
- 同一ブロック内の def→use が predecessor snapshot を見てしまう
- これは次フェーズで resolve_cur / resolve_incoming 分離で修正

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

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

src/llvm_py/llvm_builder.py

@@ -119,7 +119,10 @@ class NyashLLVMBuilder:
         
         # Resolver for unified value resolution
         self.resolver = Resolver(self.vmap, self.bb_map)
-        
+        # P0-1: Connect builder's SSOT structures to resolver
+        self.resolver.def_blocks = self.def_blocks
+        self.resolver.block_end_values = self.block_end_values
+
         # Statistics
         self.loop_count = 0
         # Heuristics for minor gated fixes