fix(tui): swallow 404 when auto-syncing referenced subagent session

The Task tool component auto-syncs the referenced subagent session in
onMount. The sync calls sdk.client.session.get with throwOnError: true,
which throws Session not found if the subagent session has been deleted.

Because the call is fire-and-forget (`void sync.session.sync(...)`), the
rejection becomes an unhandled rejection on the TUI process, which logs
"process error" and exits with code 1. A single orphaned subagent task
in the message history is enough to make the parent session unloadable.

Swallow the rejection at the call site. Sessions whose subagent rows are
gone simply render without the inlined subagent message preview, which
is the same behavior as before sync resolves.

Author: sjawhar

packages/opencode/src/cli/cmd/tui/routes/session/index.tsx

@@ -2061,8 +2061,11 @@ function Task(props: ToolProps<typeof TaskTool>) {
   const sync = useSync()
 
   onMount(() => {
-    if (props.metadata.sessionId && !sync.data.message[props.metadata.sessionId]?.length)
-      void sync.session.sync(props.metadata.sessionId)
+    const sessionId = props.metadata.sessionId
+    if (!sessionId || sync.data.message[sessionId]?.length) return
+    // Subagent sessions can be removed (deleted, cleaned up, never persisted),
+    // so swallow 404s here; the Task tool still renders without a message preview.
+    sync.session.sync(sessionId).catch(() => {})
   })
 
   const messages = createMemo(() => sync.data.message[props.metadata.sessionId ?? ""] ?? [])