[Feature] skip table lookup for meta-columns-only vector search

### Search before asking

- [x] I searched in the [issues](https://github.com/apache/paimon/issues) and found nothing similar.

### Motivation

skip table lookup for meta-columns-only vector search since row ids and scores are already available from the index result

### Solution

_No response_

### Anything else?

_No response_

### Are you willing to submit a PR?

- [x] I'm willing to submit a PR!

No files or tests are named. Start by locating the Java vector-search implementation and the path that performs table lookup after an index result; verify how meta-columns-only queries are handled. Done means those queries use the index's row IDs and scores without a table lookup, with existing behavior preserved for other queries.

Written by the indexing model from the issue text.