Artifact publishing reworks how root and served paths work, and drops PR review pages

What

An Artifact is a page Claude publishes for you, such as a small app or report, and an Artifact type is a template it can be made from. How Claude publishes them has changed.

• root: the description of this field now says a data file_path is served at its path relative to root, unless a files entry states its served path. root never changes the published path of a files entry. Claude is told to send root with every publish of an Artifact made from a type, set to the folder that holds the Artifact's files at their served paths.
• Updates: the instructions for Artifact types now tell Claude to resend the same url and a root on later changes. After creating from a type, the result mentions served_at and served_root and tells Claude to pass root or state the served path in files when updating. Before, it said to publish the same file_path again or pass url.
• Clearer errors: new detailed "nothing was published" errors cover cases such as a file sitting in the scratchpad while root is outside it, or a path that is not under root. A new type_file_path_misplaced refusal is added.
• Richer results: typed publishes now report served_at, served_root, new_files and unchanged_files, built from the server's list of the Artifact's live paths (liveOwnPaths). Unchanged files are matched by a sha256 fingerprint.
• PR review removed: the pr_review field, the composedPrReview option, the prReviewSlugs overwrite guard and errors such as review_single_file, pr_review_overwrite_unverifiable and "edits can't accompany pr_review" are gone. The error for extra fields on a type_url publish now lists only url, capabilities, contract, deadline and force.
• Permission prompt: the prompt for creating from a type can now carry an extra note and a personOnly flag.

Why

These changes should cut down on files being published at the wrong path, and give Claude clearer instructions when it updates an Artifact. If you used Claude to publish composed PR review pages through the Artifact tool, that is no longer available.