test+a11y: fix mocks/expectations for source-priority + dashboard ids; pair coach-memory spinner with motion-reduce

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/settings/coach-memory-section.tsx

@@ -172,7 +172,10 @@ export function CoachMemorySection({
                 disabled={!isAuthenticated || forgetAll.isPending}
               >
                 {forgetAll.isPending ? (
-                  <Loader2 className="size-4 animate-spin" aria-hidden />
+                  <Loader2
+                    className="size-4 animate-spin motion-reduce:animate-none"
+                    aria-hidden
+                  />
                 ) : (
                   <Trash2 className="size-4" aria-hidden />
                 )}