Fix ordered SQL Server UNION branches

[elpete]

Closes #201

What changed

• compile independently ordered and limited SQL Server UNION branches as derived queries
• preserve TOP and ORDER BY within each branch so each source contributes its intended top rows
• retain the existing compilation and validation behavior for ordinary UNION queries
• add a regression test based on the issue reproduction

Root cause

qb treated the root orderBy() as the final UNION ordering and rejected every orderBy() on a unioned builder. SQL Server can support the requested top-N-per-source operation, but each ordered TOP query must be isolated as a derived query rather than emitted directly as a UNION operand.

Validation

• TestBox on Lucee 6: 2,773 passed, 0 failed, 3 skipped
• box run-script format:check
• git diff --check