agent ui: stop pause/resume from navigating to hive-c0re's raw response

pauseAction.ts submitted a real <form> POST, so clicking pause/resume
navigated the whole page to hive-c0re's plain-text "ok" response body
instead of staying on the agent terminal. Switch to a fetch with
mode: 'no-cors' (still cross-origin-safe, no CORS headers needed from
hive-c0re) + credentials: 'include' to match the form's cookie
behavior, then refresh() the agent state afterward, matching the
existing postModel/postEffort pattern right next to it in Root.tsx.

frontend/packages/agent/src/Root.tsx

@@ -202,7 +202,9 @@ export function Root() {
           costLabel={cost !== null ? fmtTokens(cost) : undefined}
           paused={state.paused}
           onTogglePause={() => {
-            submitPauseResume(resolveDashboardBase(state.dashboard_port), state.label, state.paused ? 'resume' : 'pause');
+            submitPauseResume(resolveDashboardBase(state.dashboard_port), state.label, state.paused ? 'resume' : 'pause').then(
+              () => refresh(),
+            );
           }}
         />
       </Header>