v0.14.0 — V4 headerless wire format (breaking)

V4 headerless wire format — profile_index in the bootstrap marker

⚠️ Breaking change. V4 is a hard incompatible wire-format break with V3 (≤ 0.13.18): both ends must run 0.14.0. An older receiver will not decode a 0.14.0 transmitter (and vice-versa) — it fails cleanly (no header where it expects one), it does not mis-decode.

Why

Through the relay, HIGH+ never activated in auto-detect (it decoded 98/98 when the profile was forced). Root cause: the LMS warmup sat before the protocol header, but the warmup constellation depends on profile_index — only known after the header. The auto-detect anchor pass trained the FFE on the warmup with the wrong (anchor) constellation and corrupted the QPSK Golay header, so profile_index was never read. 0.13.18 patched this with a two-pass FFE; 0.14.0 removes the cause structurally.

What changed

• The protocol header is dropped. Its only live field, profile_index, moves into the bootstrap marker (which self-equalises via its own sync — strictly more robust than the old header). New burst layout:
  PREAMBLE → MARKER(profile_index, META) → WARMUP → META_CW → [MARKER → 2·CW]*
• The RX reads the profile from the marker before training the FFE on the warmup → no more anchor-profile guessing, no two-pass fragility. Every segment is now self-describing, so re-entry after a channel outage is faster.
• Marker payload (still 12 B / 96 symbols) gains profile_index + fmt_version + an EOT_FRAME flag; the EOT frame is headerless too.
• Bonus: fixed a latent drift-estimator bug (the marker-fit Gardner now accounts for periodic preamble re-insertions).

Also in this release

• fix(rx): widened sliding-window for slow ROBUST/ULTRA profiles.
• chore(gui): bundle rtlsdr.dll as a Tauri resource (Windows builds).
• docs(gui): document the collector HMAC secret in BUILD_DEBIAN.

Validation (offline)

• modem-core 154/154 (loopback all profiles, marker, frame, drift).
• Channel-sim + chunk-injection worker harness: HIGH / HIGH+ / HIGH++ all auto-detect and decode bit-exact, 0 codewords lost (every TX codeword recovered, RaptorQ repair not even needed).
• Pending: OTA both-ends retest through the relay (coordinate a correspondent, both on 0.14.0).

Assets (amd64 / Linux desktop)

• nbfm-modem-gui_0.14.0_amd64.deb
• nbfm-modem-gui_0.14.0_amd64.AppImage

arm64 / Raspberry Pi builds are produced separately on the Pi.