forge: prose-quality audit pass + anti-repetition directives

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.

migrations/0010_prose_audit.sql

@@ -0,0 +1,20 @@
+-- The prose-quality audit pass: a QC gate that reads a finished
+-- story end to end and flags repetition, template tics, self-
+-- restatement and continuity drift before it goes to narration.
+-- Repetition a silent reader skims is glaring once narrated aloud.
+
+-- Allow 'prose_audit' as a generation_runs.kind.
+ALTER TABLE generation_runs DROP CONSTRAINT generation_runs_kind_check;
+ALTER TABLE generation_runs ADD CONSTRAINT generation_runs_kind_check
+    CHECK (kind = ANY (ARRAY[
+        'gen', 'cleanup', 'audit', 'summary', 'embed',
+        'narrate_prep', 'rewrite', 'prose_audit'
+    ]));
+
+-- 'repetition' is a first-class audit finding area.
+ALTER TABLE audit_findings DROP CONSTRAINT audit_findings_area_check;
+ALTER TABLE audit_findings ADD CONSTRAINT audit_findings_area_check
+    CHECK (area = ANY (ARRAY[
+        'character', 'continuity', 'tone', 'fact',
+        'timeline', 'repetition', 'other'
+    ]));