wip(mir): StaticCompiler receiver正規化の部分的修正 - 将来の根治に向けた基盤整備

【修正内容】
1. src/mir/builder/calls/guard.rs
   - receiver型情報がない場合のpass-through処理追加
   - ME-CALL として後段処理に委譲

2. src/mir/builder/ssa/local.rs
   - receiver kind で型情報がない場合、origin から型を推論
   - value_types への伝播を強化

【現状】
- 完全な根治には至っていない（MIR builder設計レベルの複雑な依存関係）
- .hako側workaround (51d53c29) が実用的な解決策として機能中

【根本原因】
- value_origin_newbox に ParserBox が保持される
- value_types に実際の型（String等）が欠落
- receiver に型情報がないまま StaticCompiler Method に解決される問題

【今後の方向性】
- MIR builder の型伝播システム全体の見直しが必要
- Phase 25.1: Stage-1 bridge receiver bug (partial fix)

src/mir/builder/calls/guard.rs

@@ -59,11 +59,11 @@ impl<'a> CalleeGuardBox<'a> {
         {
             // Only apply guard if box_kind is StaticCompiler
             if box_kind == CalleeBoxKind::StaticCompiler {
-                // Check if receiver has a Box type
-                if let Some(MirType::Box(receiver_box)) = self.value_types.get(&recv) {
                 let trace_enabled =
                     std::env::var("NYASH_CALLEE_RESOLVE_TRACE").ok().as_deref() == Some("1");
 
+                // Check if receiver has a Box type
+                if let Some(MirType::Box(receiver_box)) = self.value_types.get(&recv) {
                     // If receiver box type matches the static box name, this is a me-call
                     // Let it through for static method lowering (don't normalize)
                     if receiver_box == box_name {
@@ -97,6 +97,20 @@ impl<'a> CalleeGuardBox<'a> {
                         certainty,
                         box_kind: CalleeBoxKind::RuntimeData, // Switch to runtime
                     });
+                } else {
+                    // StaticCompiler Method but receiver has NO Box type
+                    // → Pass through as ME-CALL (let downstream handle it)
+                    if trace_enabled {
+                        eprintln!("[static-runtime-guard] StaticCompiler receiver has NO Box type:");
+                        eprintln!(
+                            "  {}.{} receiver %{} has no type info",
+                            box_name, method, recv.0
+                        );
+                        eprintln!("  → Passing through as ME-CALL (downstream will resolve)");
+                    }
+
+                    // Pass through unchanged - let finalize_method_receiver() handle it
+                    return Ok(callee);
                 }
             }
         }

src/mir/builder/ssa/local.rs

@@ -116,7 +116,13 @@ pub fn ensure(builder: &mut MirBuilder, v: ValueId, kind: LocalKind) -> ValueId
             builder.value_types.insert(loc, t);
         }
         if let Some(cls) = builder.value_origin_newbox.get(&v).cloned() {
-            builder.value_origin_newbox.insert(loc, cls);
+            builder.value_origin_newbox.insert(loc, cls.clone());
+
+            // CRITICAL FIX: For receiver kind, if type is missing but origin exists,
+            // infer MirType::Box from origin
+            if kind == LocalKind::Recv && builder.value_types.get(&loc).is_none() {
+                builder.value_types.insert(loc, crate::mir::MirType::Box(cls));
+            }
         }
         builder.local_ssa_map.insert(key, loc);
         loc