fix(milestone-interview): reconnect SSE stream after submitting response

Same bug as MissionInterviewModal: handleSubmitResponse was calling the
API without first reconnecting to the SSE stream. The stream's complete
event closes the connection after each question delivery, so after the
user submits an answer, a fresh connection is needed to receive the
next question or summary.

Also cleans up the stream on API error, matching MissionInterviewModal.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/dashboard/app/components/MilestoneSliceInterviewModal.tsx

@@ -330,13 +330,16 @@ export function MilestoneSliceInterviewModal({
       setStreamingOutput("");
 
       try {
+        connectToInterviewStream(sessionId);
         await respondToInterview(sessionId, responses, projectId, sessionTabId);
       } catch (err: any) {
+        streamConnectionRef.current?.close();
+        streamConnectionRef.current = null;
         setError(err.message || "Failed to submit response");
         setView({ type: "question", sessionId, question: view.question });
       }
     },
-    [projectId, respondToInterview, sessionTabId, view],
+    [connectToInterviewStream, projectId, respondToInterview, sessionTabId, view],
   );
 
   const handleApply = useCallback(async () => {