story hook: add talent attribution; normalize topics; clamp confidence
Close three schema/normalization gaps in the storyteller post-hook.
Writes record story.talent from context name; topics are stripped,
lowercased, deduped, capped at 10; confidence is clamped to [0,1]
instead of dropping out-of-range rows. NaN, non-numeric, and bool
confidence still reject. Delete the orphaned design doc the refactor
was handed from.