All major TX parameters are now hot-swappable during transmission:
- DSP params (drive, stereo, pilot, RDS levels, limiter) via
 atomic.Pointer[LiveParams], loaded once per chunk (~50ms)
- RDS text (PS, RT) via atomic.Value in encoder, applied at
 RDS group boundaries (~88ms)
- TX frequency via driver.Tune(), applied between chunks

Zero locks in DSP path. HTTP handler writes atomics, run loop
reads them. Validation happens before store.

New: SoapyDriver.Tune() for live frequency changes.
New: LiveConfigUpdate/LivePatch types for type-safe patching.
New: 4 engine tests for live DSP/freq/RDS updates + validation.

feat: add production-grade FMUpsampler (not yet wired)

Keep frame sequence numbers monotonic, lock the RDS carrier to the exact pilot phase used by the stereo encoder, and apply the accompanying DSP/control cleanups needed for stable live transmission behaviour.

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.