Add FT8 DXpedition Hound mode (work a Fox)

[patrickrb]

FT8 DXpedition "Hound" mode

Adds the Hound side of FT8 DXpedition (Fox/Hound) mode — the high-value path that lets a phone user work a rare DXpedition "Fox." Protocol verified against K1JT's official FT8 DXpedition Mode User Guide (WSJT-X 1.9).

How it works

1. Tune the rig to the Fox's published dial frequency, tap the new DX chip in the TX strip, enter the Fox's callsign, and Start.
2. The app calls the Fox high (1000–4000 Hz) with a standard grid-call, locked to the odd slot.
3. When the Fox answers (either a standard <me> <fox> -rpt or the DXpedition combo <other> RR73; <me> <hash> -rpt), the app auto-QSYs down to the frequency the Fox called us on and replies <fox> <me> R-rpt.
4. On RR73 (the combo where our call is the acknowledged one), the QSO is logged and TX stops.

Why this is small / low-risk

A decode spike (against a WSJT-X ft8code-generated reference frame, played through the app's decoder on-device) proved the Fox combo message (i3=0/n3=1) already decodes and surfaces to Java with callsignTo / dx_call_to2 / report / Fox-hash populated. And the Hound only ever transmits standard i3=1 messages (grid-call + R+rpt), which already encode. So:

• No native/DSP changes. No decoder work, no message-codec work, no multi-signal mixing.
• The Hound QSO handler is gated behind houndMode — the existing standard auto-sequencer is untouched.

Changes

• Ft8Message — fix a cosmetic double-sign (--18) in the existing i3=0/n3=1 formatter.
• GeneralVariables — houndMode + houndFoxCall flags.
• FT8TransmitSignal — startHound() + handleHoundCycle(); reuses getFunctionCommand orders 1/3 and the proven doComplete() logging.
• MainViewModel — startHoundMode() / stopHoundMode() (disables Hunt; the two are mutually exclusive).
• TxStrip — new DX chip; FT8USApp — HoundSetupSheet (Fox call + call frequency).

Verification

• ✅ Builds, installs, launches on a Pixel 8 without crash.
• ✅ DX chip renders and opens the setup sheet; entering a Fox call + Start logs HOUND: start … slot=1.
• ✅ Transmits the grid-call in the odd slot every cycle (QSO: TX slot=1 order=1 msg=[<fox> K1AF EM28]), with Hunt auto-disabled.
• ⏳ Full QSO sequencing (invite → auto-QSY → R+rpt → RR73 → log) reuses proven primitives and the spike-verified decode path, but awaits on-air validation against a live Fox (can't be exercised without a real DXpedition or a callsign-matched injection harness).

Follow-ups (intentionally out of scope)

• Polish: decoding-✓-gated CALL button, auto-QSY waterfall animation, 2-min re-arm countdown chip, directed-CQ guard, ±300 Hz R+rpt retry.
• Fox mode (run a pileup) — designed but deferred; needs the combo encoder + multi-signal mixing.

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 2.08333% with 141 lines in your changes missing coverage. Please review.
✅ Project coverage is 6.37%. Comparing base (cc3a1a9) to head (4d9f941).
⚠️ Report is 16 commits behind head on dev.

Files with missing lines	Patch %	Lines
...om/bg7yoz/ft8cn/ft8transmit/FT8TransmitSignal.java	0.00%	54 Missing ⚠️
...adio/ks3ckc/ft8us/ui/components/HoundSetupSheet.kt	0.00%	33 Missing ⚠️
...app/src/main/kotlin/radio/ks3ckc/ft8us/FT8USApp.kt	0.00%	23 Missing ⚠️
...kotlin/radio/ks3ckc/ft8us/ui/components/TxStrip.kt	0.00%	20 Missing ⚠️
.../src/main/java/com/bg7yoz/ft8cn/MainViewModel.java	0.00%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##               dev    #162      +/-   ##
==========================================
+ Coverage     6.24%   6.37%   +0.12%     
- Complexity     669     681      +12     
==========================================
  Files          267     269       +2     
  Lines        30584   30979     +395     
  Branches      4763    4856      +93     
==========================================
+ Hits          1910    1974      +64     
- Misses       28533   28864     +331     
  Partials       141     141              

Files with missing lines	Coverage Δ
...app/src/main/java/com/bg7yoz/ft8cn/Ft8Message.java	42.45% <100.00%> (+2.35%)	⬆️
...c/main/java/com/bg7yoz/ft8cn/GeneralVariables.java	34.52% <100.00%> (+0.47%)	⬆️
.../src/main/java/com/bg7yoz/ft8cn/MainViewModel.java	0.00% <0.00%> (ø)
...kotlin/radio/ks3ckc/ft8us/ui/components/TxStrip.kt	0.00% <0.00%> (ø)
...app/src/main/kotlin/radio/ks3ckc/ft8us/FT8USApp.kt	0.00% <0.00%> (ø)
...adio/ks3ckc/ft8us/ui/components/HoundSetupSheet.kt	0.00% <0.00%> (ø)
...om/bg7yoz/ft8cn/ft8transmit/FT8TransmitSignal.java	2.99% <0.00%> (+0.60%)	⬆️

... and 10 files with indirect coverage changes

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[Copilot]

Pull request overview

This PR introduces the FT8 DXpedition “Hound” mode flow (work a Fox) into the app, adding UI affordances and a dedicated transmit/decode cycle handler gated behind GeneralVariables.houndMode.

Changes:

• Adds a new DX toggle + setup dialog to start/stop Hound mode from the Compose UI.
• Adds houndMode / houndFoxCall globals and wiring in MainViewModel to enter/exit the mode.
• Implements a Hound-specific per-cycle handler in FT8TransmitSignal and fixes DXpedition combo text formatting in Ft8Message.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
ft8cn/app/src/main/kotlin/radio/ks3ckc/ft8us/ui/components/TxStrip.kt	Adds a DX toggle pill to the TX strip UI.
ft8cn/app/src/main/kotlin/radio/ks3ckc/ft8us/ui/components/HoundSetupSheet.kt	New dialog to collect Fox callsign + initial call frequency.
ft8cn/app/src/main/kotlin/radio/ks3ckc/ft8us/FT8USApp.kt	Wires DX toggle + setup sheet into the app UI flow; start/stop hooks.
ft8cn/app/src/main/java/com/bg7yoz/ft8cn/MainViewModel.java	Adds startHoundMode() / stopHoundMode() entry points.
ft8cn/app/src/main/java/com/bg7yoz/ft8cn/GeneralVariables.java	Adds houndMode and houndFoxCall global flags.
ft8cn/app/src/main/java/com/bg7yoz/ft8cn/ft8transmit/FT8TransmitSignal.java	Routes decoding cycles to a new Hound handler and adds Hound TX logic.
ft8cn/app/src/main/java/com/bg7yoz/ft8cn/Ft8Message.java	Fixes DXpedition combo message formatting to avoid double-sign reports.

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