[Feature] asTreeCte支持额外列

```sql
WITH RECURSIVE tree AS (
SELECT
id,
parent_id,
id AS root_id -- 额外列
FROM table
WHERE parent_id IS NULL

UNION ALL

SELECT
t.id,
t.parentId,
p.root_id
FROM table t
INNER JOIN tree p ON t.parent_id = p.id
)
```

Start by locating the asTreeCte entry point and the code that builds its recursive CTE query. Compare the generated anchor and recursive parts with the SQL example, then identify the relevant tests or add coverage showing that an extra root_id-style column is retained in the result.

Written by the indexing model from the issue text.