update umbra - #1162

Update the Umbra ClickBench definition: drop the primary key, ingest from
the Athena hits.parquet via the umbra.parquetview table function (instead
of a TSV COPY), and store the table with zstd compression (create.sql, the
Docker variant, reads /data/hits.parquet from the bind mount).

Switch the dataset download to hits.parquet (BENCH_DOWNLOAD_SCRIPT) to
match, require the loaded row count to equal exactly 99,997,497 (a partial
load otherwise sails through with implausibly fast timings on the
surviving subset), and run the Docker container --privileged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>