Artifact and file-listing requests can ask for a read-back

What

A new read-back option appears in several places where Claude Code talks to remote artifacts (content Claude publishes or shares) and connected resources:

• The artifact frame boot request takes a new readBack option, which adds &readback=1 to the /api/frame/... address.
• The check run before a remote action now receives an options object, { readBack: h.action === "list_files" }, so list_files actions ask for a read-back. Before, it was called with only the slug, context and action.
• artifact_share_status success reports can now carry read_back: true.
• Separately, inherited task-notification turns now mark their origin with producer: "session-task".

Why

In practice, a read-back asks for the state to be read again rather than taken from what was assumed, so file listings and artifact checks may reflect what is actually there right after a change.