Move pause check from SV_Frame (which blocked connection handshake)
into SVD_PlaybackFrame. The server runs frames normally so clients
can connect and load, but demo data isn't consumed until a client
reaches CS_ACTIVE. The spectator sees the demo from the very first
frame without missing any gameplay.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>