Adds `skald audit --story <id>`: a whole-story QC pass that reads
every chapter end to end and flags repetition, template tics,
self-restatement and continuity drift — the gate before a story
goes to narration, where repetition a silent reader skims is
glaring read aloud. Runs at max effort (real reasoning work,
worth the spend); findings land in audit_findings and print.
Also hardens the gen + cleanup directives to hunt repetition at
the source: re-phrase recurring motifs fresh, no stacked template
anaphora, dialogue echoed verbatim at most once.
Migration 0010: 'prose_audit' generation_runs.kind, 'repetition'
audit_findings.area.