fix(rules): the third row literal — fetchRules builds a list row too (#3029)

vue-tsc caught what I missed: there were THREE places hand-building a rule
list row, not two. fetchRules mapped full rules down to the same four fields
in a spot far from the other two, so consolidating the pair I could see left
this one behind — which is precisely how the server side ended up with three
divergent trim dicts in the first place.

All three now go through toHeader.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

frontend/src/stores/rulebooks.ts

@@ -35,9 +35,7 @@ export const useRulebooksStore = defineStore("rulebooks", () => {
   async function fetchRules(topicId: number) {
     try {
       const rules = await api.listRules({ topic_id: topicId });
-      rulesByTopic.value[topicId] = rules.map((r) => ({
-        id: r.id, title: r.title, statement: r.statement, topic_id: r.topic_id,
-      }));
+      rulesByTopic.value[topicId] = rules.map(toHeader);
     } catch (e) {
       useToastStore().show("Failed to load rules", "error");
       throw e;