iOS: DigiRig Data-VOX operation + FT-891 (audio-only, no CAT)

[patrickrb]

What

iOS/iPadOS can't access USB-serial CAT, so the FT-891 runs audio-only through a DigiRig with the radio's Data-VOX keying on the transmit audio. This makes that path actually work and adds the FT-891.

1. Adaptive audio routing (the functional fix). The session was .playAndRecord with .defaultToSpeaker, which pins output to the built-in speaker — so TX audio never reached the DigiRig's USB output and Data-VOX never keyed. New pure AudioSessionPolicy.playAndRecordOptions(usbAudioConnected:) drops .defaultToSpeaker when a USB audio device is present (output follows to the DigiRig, feeding the radio) and keeps it when none is (bare iPhone/iPad RX stays audible — no regression). AudioCaptureService applies it at start() and re-applies on route change so a DigiRig attach/detach flips the behavior; loop-guarded (ignores category/override reasons, only re-sets when options differ), and clears a stuck builtInSpeaker override only while USB is active.
2. Honest PTT UI. Only VOX is selectable now — CAT/RTS/DTR PTT need a wired CAT link iOS won't allow over USB. The enum cases are kept (a future Wi-Fi/rigctld bridge could use them); a persisted non-VOX value coerces to VOX; a footer explains it.
3. FT-891 added to the rig picker.
4. Data-VOX setup hint in Radio & Audio settings (connect DigiRig over USB-C, select as Input + Output, enable Data-VOX + VOX gain on the radio, PTT = VOX).

Tests

597 FT8AFKit tests pass (2 new AudioSessionPolicyTests) + 7 new app tests in a new FT8AFTests target (RigModelTests FT-891 present/round-trip, PttModeTests selectable == [.vox], AudioCaptureSessionOptionsTests neutral→AVAudioSession.CategoryOptions). App builds. xcodegen regenerated for the new file + test target/scheme.

On-device verification pending

USB output routing is device behavior — with a DigiRig + FT-891 attached, confirm TX audio leaves via USB (not the speaker), the FT-891's Data-VOX keys on the FT8 tones, and the transmission is decodable/spotted; and that attach/detach flips output between speaker and USB.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 41.77%. Comparing base (d24b408) to head (cb6f53c).
⚠️ Report is 6 commits behind head on dev.

Additional details and impacted files

@@             Coverage Diff              @@
##                dev     #751      +/-   ##
============================================
+ Coverage     41.69%   41.77%   +0.08%     
  Complexity      284      284              
============================================
  Files           278      280       +2     
  Lines         32960    33006      +46     
  Branches       3940     3940              
============================================
+ Hits          13742    13788      +46     
  Misses        18868    18868              
  Partials        350      350              

Flag	Coverage Δ
ios	97.70% <100.00%> (+0.01%)	⬆️
native	9.93% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...FT8AFKit/Sources/FT8Audio/AudioSessionPolicy.swift	100.00% <100.00%> (ø)
.../Tests/FT8AudioTests/AudioSessionPolicyTests.swift	100.00% <100.00%> (ø)

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[Copilot]

🟡 Changes recommended

Cold-start USB detection precedes session activation, while legacy non-VOX settings are masked rather than normalized.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Enables iOS DigiRig Data-VOX operation by adapting audio routing and adding FT-891 support.

Changes:

• Routes TX audio to connected USB interfaces.
• Restricts iOS PTT selection to VOX and adds setup guidance.
• Adds FT-891 and app-level tests.

File summaries

File	Description
AudioSessionPolicyTests.swift	Tests USB routing policy.
AudioSessionPolicy.swift	Defines platform-neutral session options.
project.yml	Adds the app test target and scheme.
RigModelTests.swift	Tests FT-891 persistence.
PttModeTests.swift	Tests selectable PTT modes.
AudioCaptureSessionOptionsTests.swift	Tests AVFoundation option mapping.
TransmissionSettings.swift	Restricts the PTT picker to VOX.
RadioAudioSettings.swift	Adds DigiRig setup guidance.
AudioCaptureService.swift	Applies routing policy on startup and route changes.
AppState.swift	Adds FT-891 and selectable PTT metadata.
FT8AF.xscheme	Registers app tests with the scheme.
project.pbxproj	Adds generated test-target configuration.

Review details

• Files reviewed: 12/12 changed files
• Comments generated: 4
• Review effort level: Balanced

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