Direct indexed access

import signal_dataset as sds

dataset = sds.open("gs://example-bucket/captures.sds")

descriptor = dataset.record_metadata[42]  # metadata shard only
record = dataset[42]  # signal data shard
annotation = dataset.annotations["review-v1"][42]

The reader loads root.json and its pinned snapshot at open time. It fetches manifest pages lazily and retains at most StorageOptions.manifest_cache_pages pages. Each manifest entry pins an exact data shard, aligned metadata shard, generation, size, and global ordinal range.

No read path discovers membership by listing a directory or GCS prefix.