fix: resolve ultrabrain review findings

- Remove runtime-fallback gate from session.status retry handler — runtime-fallback
  has no session.status handler, so gating it causes retry signals to be silently dropped
- Fix background_output full_session arg description: default is true, not false

src/plugin/event.ts

@@ -333,7 +333,7 @@ export function createEventHandler(args: {
         | { type?: string; attempt?: number; message?: string; next?: number }
         | undefined
 
-      if (sessionID && status?.type === "retry" && !isRuntimeFallbackEnabled) {
+      if (sessionID && status?.type === "retry") {
         try {
           const retryMessage = typeof status.message === "string" ? status.message : ""
           const retryKey = `${status.attempt ?? "?"}:${status.next ?? "?"}:${retryMessage}`