feat(sea): wire session-level query tags (statement-level already forwarded)

[msrathore-db]

Summary

Brings SEA query-tag handling to parity with the Thrift backend across both scopes.

Session-level (openSession({ queryTags })) — NEW

SeaBackend.openSession now serializes request.queryTags into the reserved QUERY_TAGS session conf, mirroring ThriftBackend.openSession. The kernel allowlists QUERY_TAGS and forwards it onto the SEA CreateSession session_confs. It runs after the configuration merge so queryTags takes precedence over an explicit configuration.QUERY_TAGS, per the documented contract. Previously SeaBackend.openSession ignored request.queryTags entirely (only configuration was forwarded).

Verified on a live warehouse (mitmproxy capture) that QUERY_TAGS reaches the /sessions request body.

Statement-level (executeStatement({ queryTags })) — already forwarded

SeaSessionBackend already serializes per-statement queryTags into statementConf.query_tags. That was a no-op end-to-end because the kernel dropped statement_conf before the SEA wire (confirmed via a live /statements capture). The companion kernel PR databricks/databricks-sql-kernel#150 adds the native query_tags array to ExecuteStatementRequest, so the existing driver forwarding now reaches the server.

⚠️ Dependency: statement-level query tags become functional once kernel #150 merges and KERNEL_REV is bumped. Session-level works today (the QUERY_TAGS session conf is already allowlisted). This PR intentionally does not bump KERNEL_REV.

Background (cross-driver parity)

• JDBC: query tags are session-scoped (QUERY_TAGS session conf).
• ADBC C# / pure-Python SEA: per-statement via the native SEA query_tags array.
• Before this + kernel scientific notation negative numbers #150, SEA query tags were a complete no-op on the kernel path (both Node useSEA and Python use_kernel), while Thrift sent them via confOverlay.query_tags.

Test

• openSession() serializes session-level queryTags into sessionConf.QUERY_TAGS.
• queryTags takes precedence over an explicit configuration.QUERY_TAGS.
• Statement-level forwarding (statementConf.query_tags) is already covered by existing tests.
• SEA unit suite green; tsc + prettier clean.

This pull request and its description were written by Isaac.