json-native: token positions (line/column); escape utils BMP coverage + surrogate guard; add smokes for string escapes, nested, and error cases (AST/VM)

apps/lib/json_native/lexer/token.nyash

@@ -53,6 +53,13 @@ box JsonToken {
     get_line() { return me.line }
     get_column() { return me.column }
     
+    // 位置情報の設定（トークナイザーから付与）
+    set_line_column(line, column) {
+        me.line = line
+        me.column = column
+        return me
+    }
+    
     // ===== 判定メソッド =====
     
     is_literal() {
@@ -247,4 +254,4 @@ static box TokenStats {
             i = i + 1
         }
     }
-}
+}

apps/lib/json_native/lexer/tokenizer.nyash

@@ -66,37 +66,39 @@ box JsonTokenizer {
         
         // EOF チェック
         if me.scanner.is_eof() {
-            return new JsonToken("EOF", "", me.scanner.get_position(), me.scanner.get_position())
+            return new JsonToken("EOF", "", me.scanner.get_position(), me.scanner.get_position()).set_line_column(me.scanner.get_line(), me.scanner.get_column())
         }
         
         local start_pos = me.scanner.get_position()
+        local start_line = me.scanner.get_line()
+        local start_col = me.scanner.get_column()
         local ch = me.scanner.current()
         
         // 構造文字（単一文字）
         local structural_type = me.char_to_token_type(ch)
         if structural_type != null {
             me.scanner.advance()
-            return this.create_structural_token(structural_type, start_pos)
+            return this.create_structural_token(structural_type, start_pos).set_line_column(start_line, start_col)
         }
         
         // 文字列リテラル
         if ch == "\"" {
-            return me.tokenize_string()
+            return me.tokenize_string().set_line_column(start_line, start_col)
         }
         
         // 数値リテラル
         if me.is_number_start_char(ch) {
-            return me.tokenize_number()
+            return me.tokenize_number().set_line_column(start_line, start_col)
         }
         
         // キーワード（null, true, false）
         if me.is_alpha_char(ch) {
-            return me.tokenize_keyword()
+            return me.tokenize_keyword().set_line_column(start_line, start_col)
         }
         
         // 不明な文字（エラー）
         me.scanner.advance()
-        return new JsonToken("ERROR", "Unexpected character: '" + ch + "'", start_pos, me.scanner.get_position())
+        return new JsonToken("ERROR", "Unexpected character: '" + ch + "'", start_pos, me.scanner.get_position()).set_line_column(start_line, start_col)
     }
     
     // ===== 専用トークナイザーメソッド =====