🔧 Hotfix 7 (Enhanced): ValueId receiver alias tracking for nested loops

- Problem: Pinned receiver variables in loops cause undefined ValueId errors
- Enhanced fix: Update all receiver aliases (me + all __pin$N$@recv levels)
- Handles nested loops by updating previous pin levels
- Test status: Partial improvement, ValueId(50) → ValueId(40)
- Further investigation needed for complete fix

Files modified:
- src/mir/phi_core/loopform_builder.rs (emit_header_phis)

lang/src/compiler/entry/func_scanner.hako

@@ -12,10 +12,12 @@ static box FuncScannerBox {
     return me._scan_methods(source, box_name, 1, 0)
   }
 
-  // Scan all static box definitions and collect their methods.
-  method scan_all_boxes(source) {
-    local defs = new ArrayBox()
-    local s = "" + source
+	  // Scan all static box definitions and collect their methods.
+	  method scan_all_boxes(source) {
+	    // source が null の場合はスキャン対象がないので空配列を返すよ。
+	    if source == null { return new ArrayBox() }
+	    local defs = new ArrayBox()
+	    local s = "" + source
     local n = s.length()
     local i = 0
     local in_str = 0
@@ -377,9 +379,11 @@ static box FuncScannerBox {
     return params
   }
 
-  // Helper: strip comments from source
-  method _strip_comments(source) {
-    local s = "" + source
+	  // Helper: strip comments from source
+	  method _strip_comments(source) {
+	    // source が null の場合はそのまま空文字として扱う（コメント除去する対象がないだけ）
+	    if source == null { return "" }
+	    local s = "" + source
     local out = ""
     local i = 0
     local n = s.length()