USB CAT: readable serial port picker, VID+PID device match, diagnostics hint (#817)

[patrickrb]

Partial implementation of #817, scoped to the parts that hold for every rig.

Why not the rest of #817

The issue proposed auto-selecting the CAT interface from a VID:PID table and auto-probing interfaces × baud rates when CAT is silent. Both were checked against vendor docs and deliberately not implemented:

• On the very same chip (Silicon Labs CP2105, 10C4:EA70) Yaesu (FT-891, FT-991A, FTDX10, FT-710) carries CAT on the Enhanced interface (0) and keying on Standard, while Kenwood's TS-890S manual says to use the Standard port for PC control (menu 7-01 "Baud Rate (Virtual Standard COM Port)"). Icom's IC-9700/IC-7610 also expose two ports (A = CI-V). A table keyed on the chip is wrong for someone; keying on the selected instruction set is not reliable either.
• Baud-walking on the frame-less 5-byte Yaesu protocol (FT-817/857/897) can decode garbage as an opcode, including 0x08 = PTT on. FT-710 cable mode and the Hamlib backend never answer a read, so the probe would "fail" there by design. It would also have to coexist with the auto-reconnect loop and the CAT liveness watchdog (Fix CAT chip turning red while CAT still works (#781) #818).

The app now states the facts and leaves the choice to the operator. USB auto-connect still opens the first enumerated port (interface 0 = Enhanced, right for Yaesu) and a manual pick is still not persisted, so a wrong pick self-heals on restart.

What changes

• Readable picker rows — Silicon Labs CP2105 · Port 1 of 2 · Enhanced / … Port 2 of 2 · Standard instead of \0x03E9\0x10C4\0xEA70\0x1. New pure SerialPortLabel (chip name from the driver class + PID; the role is only ever the chip's own interface name, never "CAT"/"PTT"). Same label feeds the legacy picker and the web log page through SerialPort.information().
• Dual-port hint in the picker when a CP2105 is listed: Yaesu uses Enhanced for CAT, Kenwood TS-890S/TS-990S uses Standard, the other port carries RTS/DTR keying.
• Device match by VID+PID — CableSerialPort.prepare() / isDevicePresent() matched on vendor id only and kept the last device the map iterated, so an FT-891 (CP2105) plus a Digirig (CP2102, same vendor) could open the wrong chip. Now: same deviceId+VID+PID, else first VID+PID, else (unknown PID, legacy) first vendor match. The match is logged to debug.log (serial.prepare: matched …).
• CDC-class devices are listed when no prober claims them (prepare() already fell back to CdcAcmSerialDriver, so they could connect but never appeared in the picker), gated on an actual Communications-class interface so the rig's audio codec is not offered as a port.
• USB Diagnostics: new "CAT Port" row (Port 2 of 2 · Standard · 4800 bd) and a hint under the card when the port is open but CAT is silent — the Enhanced/Standard note on a dual-port chip, a baud/model note otherwise. In FT-710 cable mode (read loop intentionally off) CAT Response is now an informational row with an explanation instead of a permanent red.

The off-by-one bounds bug listed in #817 was already fixed on dev (isValidPortIndex).

Tests

• SerialPortLabelTest (17): chip names, Enhanced/Standard for CP2105 only, never hex, never a CAT/PTT role, template fallback.
• CableSerialPortDeviceMatchTest (9): two Silicon Labs chips in either order, re-plug (new deviceId), recycled deviceId on another product, legacy vendor-only, CDC gate, FT-710 mode.
• SerialPortPickerHintTest (3).
• UsbDiagnosticsLogicTest (+14): row order, CAT Port value/template, INFO-not-FAIL for FT-710, hint selection.

Full unit suite: 3892 tests, 0 failures. Debug APK built and smoke-run on the Pixel_8 emulator (USB Diagnostics page renders the new row, no crash). Not verified on hardware — no phone was attached; a real CP2105 rig (FT-891/FT-991A) is needed to see the populated rows and the picker labels.

Closes #817 for the parts above; the auto-select and auto-probe proposals are declined with the reasoning here.

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[codecov]

Codecov Report

❌ Patch coverage is 56.97674% with 37 lines in your changes missing coverage. Please review.
✅ Project coverage is 42.04%. Comparing base (fd4db16) to head (aec7c96).

Files with missing lines	Patch %	Lines
...o/ks3ckc/ft8af/ui/settings/UsbDiagnosticsScreen.kt	62.33%	28 Missing and 1 partial ⚠️
...dio/ks3ckc/ft8af/ui/settings/RadioAudioSettings.kt	11.11%	8 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                dev     #820      +/-   ##
============================================
+ Coverage     42.00%   42.04%   +0.04%     
  Complexity      239      239              
============================================
  Files           276      276              
  Lines         33097    33177      +80     
  Branches       3850     3871      +21     
============================================
+ Hits          13902    13949      +47     
- Misses        18913    18945      +32     
- Partials        282      283       +1     

Flag	Coverage Δ
android	17.53% <56.97%> (+0.17%)	⬆️
native	9.93% <ø> (ø)

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Files with missing lines	Coverage Δ
...dio/ks3ckc/ft8af/ui/settings/RadioAudioSettings.kt	0.26% <11.11%> (+0.13%)	⬆️
...o/ks3ckc/ft8af/ui/settings/UsbDiagnosticsScreen.kt	55.75% <62.33%> (+4.13%)	⬆️

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Pull request overview

Improves USB CAT port selection, labeling, and diagnostics for multi-port and CDC devices.

Changes:

• Matches USB devices by device ID, VID, and PID.
• Adds readable serial-port labels and dual-port guidance.
• Expands USB diagnostics and unit coverage.

File summaries

File	Description
UsbDiagnosticsLogicTest.kt	Tests CAT-port diagnostics and hints.
SerialPortPickerHintTest.kt	Tests dual-port hint visibility.
SerialPortLabelTest.java	Tests readable port labels.
CableSerialPortDeviceMatchTest.java	Tests device matching and CDC detection.
strings_compose.xml	Adds diagnostics and picker text.
UsbDiagnosticsScreen.kt	Displays CAT port details and guidance.
RadioAudioSettings.kt	Uses readable picker labels.
MainViewModel.java	Exposes connected USB-port state.
SerialPortLabel.java	Generates human-readable labels.
CableSerialPort.java	Adds VID/PID matching and CDC fallback.
CableConnector.java	Retains selected-port metadata.

Review details

• Files reviewed: 11/11 changed files
• Comments generated: 5
• Review effort level: Balanced

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