v0.2.0

Breaking

• StorageProvider now requires save_stream, range-aware open_stream, iter_objects, and check_writable, and widens url with optional response controls. Provider protocols are runtime-checkable and custom backends are supported, so adding required members breaks those backends even though existing callers of save, get, and url remain source-compatible. The new members are not optional capability checks; third-party storage backends must implement the complete contract.

Added

• Bounded-memory storage I/O. save_stream consumes non-seekable sources and enforces max_bytes mid-stream; local disk writes through a temporary file, while S3 uses multipart upload and aborts it on failure. open_stream returns the same read-once, non-seekable stream contract on both backends and supports offset/length range selection. Missing objects raise FileNotFoundError.
• Lazy reconciliation via iter_objects, yielding each key with its modification epoch, and a storage-specific check_writable readiness probe.
• StorageBackendUnavailableError hides local filesystem and botocore failures, and StorageSizeLimitError identifies a streaming size-limit breach.
• S3 presigned URLs accept download_as and content_type, allowing a host to force attachment download and pin the response media type for untrusted blobs.

Changed

• The local backend warns once when URL expiry or response-header controls are requested, because those controls belong to the host web server for local://. Existing whole-object save/get behavior remains available for small blobs.