[Bug] Duplicated query comments for snapshots

[mwojcik321]

Is this a new bug in dbt-snowflake?

• I believe this is a new bug in dbt-snowflake
• I have searched the existing issues, and I could not find an existing issue for this bug

Current Behavior

Queries executed during the snapshot run contain duplicate comments:

select * from (
        select to_timestamp_ntz(convert_timezone('UTC', current_timestamp())) as dbt_snapshot_time
    ) as __dbt_sbq
    where false
    limit 0
/* {"dbt_version": "1.9.0", "invocation_id": "9f3fa140-f4e8-40a0-a0a7-cf83fadd5529", ...} */
/* {"dbt_version": "1.9.0", "invocation_id": "9f3fa140-f4e8-40a0-a0a7-cf83fadd5529", ...} */

Expected Behavior

The query comment should be added only once to the query:

select * from (
        select to_timestamp_ntz(convert_timezone('UTC', current_timestamp())) as dbt_snapshot_time
    ) as __dbt_sbq
    where false
    limit 0
/* {"dbt_version": "1.9.0", "invocation_id": "9f3fa140-f4e8-40a0-a0a7-cf83fadd5529", ...} */

Steps To Reproduce

1. Configure query comments in dbt_project.yml:

query-comment:
  comment: "{{ get_query_comment(node) }}"
  append: true  # Snowflake removes prefixed comments.

2. Add example snapshot
3. Execute dbt snapshot command

Relevant log output

No response

Environment

- OS: Linux
- Python: 3.11
- dbt-core: 1.8.4 and 1.9.0
- dbt-snowflake: 1.8.4 and 1.9.0

Additional Context

It appears that the issue is linked to the method add_select_query in the dbt-adapters package, which is responsible for adding the query comment. Subsequently, the query is processed by add_standard_query in the dbt-snowflake package, which adds another query comment.