Faster flaky test run back-marking scan

Back-marking test case runs as flaky now prunes the ClickHouse scan by also constraining git_commit_sha in the lookup, which engages the table’s GRANULARITY 1 bloom filter and limits the read to the granules containing that commit’s runs. This substantially reduces rows, memory, and time on the flaky-marking path, so cross-run flakiness back-marking settles faster and the associated slow-query alerts no longer trip.