fix: use SSEEvent type in onEvent cast instead of inline type shape (#18)

* Initial plan

* fix: use SSEEvent type in onEvent cast instead of inline type shape

Co-authored-by: intel352 <77607+intel352@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: intel352 <77607+intel352@users.noreply.github.com>

Author: Copilot

ui/src/utils/sse.ts

@@ -4,7 +4,7 @@ import type { SSEEvent } from '../types';
 export function connectSSE(onEvent: (event: SSEEvent) => void): EventSource {
   const es = sharedConnectSSE({
     url: '/events',
-    onEvent: onEvent as (event: { type: string; data: unknown; [key: string]: unknown }) => void,
+    onEvent: onEvent as (event: SSEEvent) => void,
     onError: () => {
       // Suppress SSE connection errors in console — the shared library handles reconnection
     },