Improve writer prompt testing

db/migrations/018_writer_prompt_contract_cleanup.sql

@@ -0,0 +1,25 @@
+UPDATE app_settings
+SET value_json = to_jsonb(
+  trim(
+    regexp_replace(
+      value_json #>> '{}',
+      E'\\n?OUTPUT:[[:space:]]*JSON only\\.[[:space:]]*',
+      E'\\n',
+      'gi'
+    )
+  )
+),
+updated_at = NOW()
+WHERE key = 'ai_writer_prompt'
+  AND value_json #>> '{}' ~* 'OUTPUT:[[:space:]]*JSON only\.';
+
+UPDATE app_settings
+SET value_json = to_jsonb(
+  CASE
+    WHEN value_json #>> '{}' ~* 'Return JSON only\\.'
+      THEN value_json #>> '{}'
+    ELSE trim(value_json #>> '{}') || E'\n- Return JSON only. No markdown. No text outside JSON.'
+  END
+),
+updated_at = NOW()
+WHERE key = 'ai_writer_contract';