Window expression loses OVER clause when arithmetic is chained #606

Describe the bug

In go-jet v2.15.0, chaining arithmetic after a window expression can remove the OVER clause from the left-hand operand.
This affects at least integer and float expressions:

ROW_NUMBER().
    OVER(ORDER_BY(Example.ID)).
    ADD(Int64(1))

Generated SQL:

ROW_NUMBER() + 1::bigint

PostgreSQL rejects this SQL:

pq: window function row_number requires an OVER clause
The same issue occurs with aggregate window expressions. When .SUB(...) is chained after .OVER(...), the left-hand expression loses its window clause while the right-hand expression keeps it.
An explicit wrapper works around the issue:

IntExp(
    ROW_NUMBER().OVER(ORDER_BY(Example.ID)),
).ADD(Int64(1))

This suggests that chained arithmetic uses the expression root from before the window expression was constructed.

Environment (please complete the following information):

• OS: linux , macos
• Database: PostgreSQL
• Database driver: github.com/lib/pq v1.12.3
• Jet version: github.com/go-jet/jet/v2 v2.15.0
• Go version: go1.24.2

Code snippet
The example uses a generic table generated by Jet:

package main

import (
    "fmt"

    . "github.com/go-jet/jet/v2/postgres"
    . "example/generated/table"
)

func main() {
    stmt := Example.SELECT(
        ROW_NUMBER().
            OVER(ORDER_BY(Example.ID)).
            ADD(Int64(1)),
    )

    fmt.Println(stmt.DebugSql())
}

Actual SQL:

SELECT ROW_NUMBER() + 1::bigint
FROM example

Another reproduction using aggregate window expressions:

stmt := Example.SELECT(
    SUMf(Example.Debit).
        OVER(PARTITION_BY(Example.GroupID)).
        SUB(
            SUMf(Example.Credit).
                OVER(PARTITION_BY(Example.GroupID)),
        ),
)
fmt.Println(stmt.DebugSql())

Actual SQL:

SELECT
    SUM(example.debit)
    -
    SUM(example.credit) OVER (PARTITION BY example.group_id)
FROM example

No custom model logic is involved. Example is a normal table generated by the Jet generator with these relevant columns:

id
group_id
debit
credit

Expected behavior

The complete window expression should remain the left-hand operand when arithmetic is chained.
Expected ROW_NUMBER() SQL:

SELECT
    ROW_NUMBER() OVER (ORDER BY example.id) + 1::bigint
FROM example
Expected aggregate SQL:
SELECT
    SUM(example.debit) OVER (PARTITION BY example.group_id)
    -
    SUM(example.credit) OVER (PARTITION BY example.group_id)
FROM example
Explicit IntExp(...) or FloatExp(...)

wrappers should not be required to preserve the OVER clause.