fix(llvm): Phase 131-7 - Multi-pass vmap sync 修正（Branch bug 解消）

Phase 131-7: Multi-pass block lowering の vmap sync バグ修正

問題:
- Pass A (body instructions) が vmap_cur に値を保存
- Pass C (deferred terminators) が builder.vmap を参照
- → Pass A の値が Pass C に届かない
- → Branch condition が 0 に fallback → 無限ループ

修正:
- src/llvm_py/builders/block_lower.py (lines 237-248):
  - PHI-only フィルタを削除
  - 全ての値を global vmap に sync

変更ファイル:
- src/llvm_py/builders/block_lower.py: vmap sync 修正
- src/llvm_py/instructions/controlflow/branch.py: trace logging 追加
- src/llvm_py/instructions/unop.py: trace logging 追加
- src/llvm_py/llvm_builder.py: debug helpers 追加
- src/llvm_py/phi_wiring/wiring.py: trace logging 追加
- src/runner/modes/common_util/exec.rs: Python stdout 転送

結果:
- ✅ Branch bug 修正: ループが正しく終了
- ✅ 出力: 無限ループ → 3回で停止
- ❌ 新 bug 発見: ExternCall が null を受け取る（PHI 値の代わりに）

Next: Phase 131-8 (ExternCall argument handling 修正)

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

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

src/llvm_py/instructions/controlflow/branch.py

@@ -30,7 +30,22 @@ def lower_branch(
         bb_map: Block map
     """
     # Get condition value with preference to same-block SSA
+    # Phase 131-7 debug
+    try:
+        import os, sys
+        if os.environ.get('NYASH_CLI_VERBOSE') == '1':
+            print(f"[branch] cond_vid={cond_vid} in vmap={cond_vid in vmap} (vmap id={id(vmap)})", file=sys.stderr)
+            if cond_vid in vmap:
+                print(f"[branch] vmap[{cond_vid}] = {vmap[cond_vid]}", file=sys.stderr)
+    except Exception:
+        pass
     cond = resolve_i64_strict(resolver, cond_vid, builder.block, preds, block_end_values, vmap, bb_map)
+    try:
+        import os, sys
+        if os.environ.get('NYASH_CLI_VERBOSE') == '1':
+            print(f"[branch] resolved cond={cond}", file=sys.stderr)
+    except Exception:
+        pass
     if cond is None:
         # Default to false if missing
         cond = ir.Constant(ir.IntType(1), 0)