When gallery-dl logs "[patreon][error] Failed to extract campaign ID"
but then recovers via its /cw/<vanity> fallback and skips every file
(all already archived), _categorize_error was flagging the [error] line
as fatal and returning UNKNOWN_ERROR. Add "failed to extract campaign
id" to the per-item error allowlist alongside "not allowed to view" and
"unable to get post" so skip detection proceeds and the run is
classified NO_NEW_CONTENT.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
