Captures normalized error fingerprints into the durable digest and clusters
recurring root-cause errors across sessions — closes the content-level 'why' gap
called out in the friction assessment. 3 tasks; we implement this in helix_forge.
(State Hub skill handed off to the state-hub worker as STATE-WP-0058.)
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
