fix(dashboard): defend MissionManager.loadMissions against non-array fetch results

When fetchMissions returns a non-array (envelope shape, error path, or
mocked detail object) setMissions(data) leaks the bad shape into render,
where missions.filter() throws "is not a function" and crashes the
entire MissionManager test file. Coerce to [] before storing, matching
the existing defenses on the useState init and cache-hydration paths.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/dashboard/app/components/MissionManager.tsx

@@ -811,7 +811,10 @@ export function MissionManager({ isOpen, isInline = false, onClose, addToast, pr
       if (!hasHydratedRef.current) {
         setLoading(true);
       }
-      const data = await fetchMissions(projectId);
+      const fetched = await fetchMissions(projectId);
+      // Defensive: API helpers can return an envelope or non-array under
+      // failure paths; downstream code (render, filter) assumes an array.
+      const data = Array.isArray(fetched) ? fetched : [];
       setMissions(data);
       writeCache(
         missionsCacheKey,