fix(test): increase poll timeout to fix flaky late-session-id test

WAIT_FOR_SESSION_TIMEOUT_MS of 2ms was too tight for 2 poll iterations
at 1ms intervals — setTimeout precision caused the budget to expire
before the 2nd getTask call. Bumped to 50ms.

src/tools/delegate-task/background-task.test.ts

@@ -13,7 +13,7 @@ describeFn("executeBackgroundTask output/session metadata compatibility", () =>
     //#given - reduce waiting to keep tests fast
     __setTimingConfig({
       WAIT_FOR_SESSION_INTERVAL_MS: 1,
-      WAIT_FOR_SESSION_TIMEOUT_MS: 2,
+      WAIT_FOR_SESSION_TIMEOUT_MS: 50,
     })
   })