[mkaand]

Summary

• Standardize OPFS-first staging for supported video Share / Save flows without a file-size threshold.
• Keep the existing Blob fallback only when OPFS is unavailable, while preserving Tap Again and cleanup/retry semantics.
• Preserve the accepted PR Fix Facebook URL variants and iOS share compatibility #43 prepared-Facebook-video flow; images and audio are unchanged.

Scope and safety

• Frontend-only: no backend, provider, resolver, queue, or security-boundary changes.
• Direct video delivery now streams chunk-by-chunk to OPFS when supported; no full-video JS heap materialization on that path.
• YouTube 720p+ is unrelated and not included.

Verification

• Added direct-video OPFS, fallback, unknown-total progress, size-limit, and second-tap coverage.
• PR Fix Facebook URL variants and iOS share compatibility #43 physical acceptance established the OPFS staging baseline; this PR generalizes it to all supported video flows.