parallelize gnomad_get_variant batch lookups under the concurrency cap
Batch variant lookups fan out concurrently instead of a serial loop; the existing GNOMAD_MAX_CONCURRENCY semaphore still bounds upstream GraphQL calls.
Changed:
gnomad_get_variant— batch dispatch is now concurrent (was a serial for loop), bounded by the existingGnomadServicesemaphore (GNOMAD_MAX_CONCURRENCY, default 2); per-item partial success preserved andfound[]/failed[]stay in input order. No schema change. (#10)
107 tests pass; bun run devcheck clean.