sql: type annotation does not work correctly in prepared statement

**Describe the problem**

Please describe the issue you observed, and any steps we can take to reproduce it:

Hi, the following prepared statement is equivalent to the normal statement, however, the normal statement triggers an error.

**To Reproduce**

```
PREPARE prepare_query (int8) AS SELECT DISTINCT STDDEV((($1) :::DECIMAL));
EXECUTE prepare_query(-1); -- NULL
DEALLOCATE prepare_query;
SELECT DISTINCT STDDEV((((-1)::INT8) :::DECIMAL)); -- ERROR: stddev(): incompatible type annotation for ((-1):::INT8) as decimal, found type: int
```

**Expected behavior**
No error in the normal statement.

**Additional data / screenshots**
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**Environment:**
- CockroachDB version [CockroachDB CCL v25.4.1 (x86_64-pc-linux-gnu, built 2025/11/26 12:08:42, go1.23.12 X:nocoverageredesign)]
- Server OS: [Linux]
- Client app [`cockroach sql`, JDBC]

**Additional context**
What was the impact?

Add any other context about the problem here.

Jira issue: CRDB-57611

Start by running the provided PREPARE/EXECUTE and normal SELECT statements in cockroach sql, then compare how the prepared statement and direct expression handle the DECIMAL type annotation. Done means the normal SELECT no longer reports an incompatible type annotation while preserving the prepared statement's behavior.

Written by the indexing model from the issue text.