Keep DSP state persistent across generated frames, move the RDS encoder to arbitrary sample-rate operation, and tune the Pluto profile to the working 2.28 MHz path with the levels that finally decode reliably.

Introduce CLI TX mode, hardware driver selection, IQ resampling to device rate, and platform-specific PlutoSDR/SoapySDR integrations. Update engine pacing for blocking hardware writes and refresh docs/release notes for the hardware-ready v0.6.0-pre milestone.