Include rows_before_limit_at_least in X-ClickHouse-Summary header

### Use case

I'm using fetch_bytes("RowBinaryWithNamesAndTypes") to get query results in binary format. I parse the binary response myself in Rust and use cursor.summary() (from #397) to get query statistics.

The problem is that rows_before_limit_at_least is only available when using JSON output formats (JSON, JSONStrings, etc.) because it's embedded in the JSON body. When using RowBinary, the only source of server-side stats is the X-ClickHouse-Summary HTTP header, which doesn't include this field.

### Describe the solution you'd like

Could rows_before_limit_at_least be added to the X-ClickHouse-Summary header, so that non-JSON format users can also access it?

Related #397

Start by reading cursor.summary() from #397 and tracing how the X-ClickHouse-Summary header is handled for fetch_bytes("RowBinaryWithNamesAndTypes"). Check the existing summary-related behavior and tests, if present. Done means rows_before_limit_at_least is available through the summary for non-JSON responses.

Written by the indexing model from the issue text.