test(desktop): let relay state poll retry

[santho090]

Summary

• let expect.poll retry while the E2E relay-state hook is still being installed
• keep the final assertion unchanged: the relay must still reach connected

The old callback threw when the hook was absent, which stopped the poll instead of letting it retry. This uses the same optional call pattern as the other relay-state polls in the file.

This PR addresses the order-dependent poll in #6242. The separate fixed-port environment note remains out of scope.

Related issue

Fixes #6242.

Testing

• Before the change, a temporary no-op predecessor and 10 repeats produced 1 failure and 19 passes with Relay state seam is not installed.
• With the change, the same 20-test run passed 20 of 20.
• pnpm -C desktop exec playwright test tests/e2e/relay-reconnect.spec.ts --project=smoke --workers=1: 14 passed
• pnpm -C desktop exec biome check tests/e2e/relay-reconnect.spec.ts
• pnpm -C desktop typecheck
• just ci