Tempo v0.2.0 — IR-HARQ + DX1 full-band (beta)

Tempo v0.2.0 — a beta release. This adds the two flagship modem capabilities and lands the
session's app work. It is simulation- and Windows-cross-build-validated, but not yet on-air
validated — see Status below.

✨ What's new

IR-HARQ — adaptive retransmission combining (now live, on by default)

FT1's signature feature, previously dormant, is finished end-to-end. A frame that fails to decode
on its own (RV0) is recovered by joint-turbo-combining its retransmissions (RV0→RV1→RV2 — each
with distinct Costas sync + punctured LDPC parity). The QSO sequencer drives it automatically
(escalate on implicit NAK, reset on implicit ACK).

• Measured: combiner +1.3 dB (AWGN, 3-TX) / +3.2 dB (1 Hz/1 ms fading); through the full
  live pipeline, ≈ +2.5 dB threshold shift and ~2× QSO completion in the −11…−13 dB zone.
• Reliable RV detection (coherent CPM-Costas discriminator): >99% accurate, <1% false to −11 dB.
• UI: HARQ·RVn decode badge, a HARQ on/off toggle (default on, for A/B), and a session rescue counter.

DX1 full-passband acquisition

The DX1 robust tier now decodes every signal across 200–2900 Hz in one slot (like FT1's Costas
search) instead of only the carrier under the green marker. rx_offset_hz becomes a waterfall
marker / TX-pairing hint. Internally a three-stage scan — coarse chirp-correlation carrier sweep
(12.5 Hz grid, pre-folded replicas) → median-threshold peak-pick → full CRC-gated decode per
survivor — running ~3–4 s/slot (vs ~19 min for a naive sweep on Windows; the design's
trig-free hot loop is what makes it tractable on the target).

Also in this release

• Coordinated QSY (announced, Part-97-legal channel moves), passive-launch fix, composer level
  meter, FT8/FT4 tier honesty (the unfinished tier no longer mis-advertises), FT1 docs.
• .wav replay path — turn a captured slot into a deterministic regression fixture.

✅ Validation

• FT1 AWGN 50% ≈ −15 dB; DX1 AWGN 50% ≈ −18.6 dB with a ~3.7 dB fading penalty.
• Live IR-HARQ: +2.5 dB / ~2× completion in the marginal zone.
• Cross-built and smoke-tested on Windows — all 5 modem exes pass (FT1 −15 dB, DX1 −18 dB,
  the 3-signal full-band scan, FT1 acquisition + IR-HARQ rv through the C-ABI), plus tempo.exe
  and the installer build clean.
• The full headless Rust suite is green; clippy clean; UI builds clean.

⚠️ Status — this is a beta

Everything above is proven in simulation + on the Windows cross-build. The open gate is real
RF: on-air decode-rate-vs-SNR has not been measured. If you run it on the air, please share
reports in Discussions — that's the feedback the
project most needs.

📦 Install (Windows x64)

1. Download Tempo_0.2.0_x64-setup.exe and run it. The installer bundles the offline WebView2
   runtime + Hamlib (rigctld), so CAT works with no separate install.
2. Optional: win_smoke.exe — a fully-static modem self-test (FT1 + DX1 round-trip; runs
   anywhere, no install). dx1_band_test_standalone.exe demonstrates the new full-band scan
   (3 signals decoded in one slot).