🐛 fix(oracle): 修复DDL注释拼接缺少分号与换行

- 为 Oracle 建表 DDL 追加注释前补齐语句结束符并保留空行分隔
- 修复 COMMENT ON TABLE/COLUMN 与 CREATE TABLE 粘连导致复制后无法直接执行的问题
- 补充后端 Oracle 建表语句与前端 DDL 格式化回归测试

internal/db/oracle_get_tables_test.go

@@ -317,4 +317,7 @@ ORDER BY c.column_id`] = oracleRecordingQueryResult{
 			t.Fatalf("expected DDL to contain %q, got: %s", want, ddl)
 		}
 	}
+	if !strings.Contains(ddl, ");\n\nCOMMENT ON TABLE") {
+		t.Fatalf("expected Oracle DDL comments to be separated by a statement terminator and blank line, got: %s", ddl)
+	}
 }