Add FT4 mode (extensible to future modes)

[patrickrb]

What

Adds FT4 as a selectable operating mode alongside FT8. The design is built around a new ModeProfile descriptor so a future mode (e.g. FT2) is a one-entry add, not another FT8/FT4 boolean.

Highlights

• Mode button on the decode page (pill in TxStrip, disabled mid-TX). Cycles FT8↔FT4 via MainViewModel.setOperatingMode, persisted across restarts.
• FT4 TX + RX. FT4 decode was already supported by the prebuilt libft8cn.so (InitDecoder protocol flag). FT4 encode had no JNI entry point in the prebuilt, so a small shim (cpp/ft4_encode_jni.cpp) compiled into the CMake-built libft8af_usb.so bridges to the prebuilt's raw ft4_encode (linked via an IMPORTED target; DT_NEEDED libft8cn.so). See the inline comment for how to remove it once the native reconstruction replaces the prebuilt.
• Radio-safety: switching mode retunes the dial within the same band only (FT8 14.074 → FT4 14.080). It never auto-QSYs to a band the user may not have tuned (high-SWR PA-damage risk). Bands with no FT4 allocation (160m/60m) keep their frequency.
• Timing generalized: UtcTimer.sequential(utc, slotMillis) (FT8 output byte-identical), per-mode cycle timers rebuilt on switch, per-mode late-start/Costas-clip slack, SlotTimerBar parameterized by slot length.
• Mode strings (QSL log, SWL log, PSKReporter query, POTA self-spot) now derive from ModeProfile.displayName.
• Bands: mode-tagged FT4 dials added to bands.txt; frequency/settings pickers filter by current mode.

Tests

• New ModeProfileTest (descriptor table, fromId fallback), OperationBand FT4 parsing + getModeBandFreq, UtcTimer.sequential per-mode.
• Full testDebugUnitTest green; native build links across all 4 ABIs; installed on a Pixel 8 and both native libs load with no UnsatisfiedLinkError.

Manual verification still needed (requires RF)

• Decode FT4 off-air on an FT4 sub-band (e.g. 14.080) → spots tagged FT4
• TX FT4 into a second rig running WSJT-X FT4 → decodable (validates Costas timing + per-mode slack)
• Confirm PSKReporter shows FT4 spots

Note

The native reconstruction sources (cpp/ft8_lib, cpp/ft8cn_glue, cpp/libsamplerate) remain untracked per existing project convention; this PR does not touch them. FT4 ships via the prebuilt + the new ft8af_usb shim.

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 19.41176% with 137 lines in your changes missing coverage. Please review.
✅ Project coverage is 6.58%. Comparing base (07fff06) to head (fd10605).
⚠️ Report is 4 commits behind head on dev.

Files with missing lines	Patch %	Lines
.../src/main/java/com/bg7yoz/ft8cn/MainViewModel.java	0.00%	33 Missing ⚠️
...app/src/main/kotlin/radio/ks3ckc/ft8us/FT8USApp.kt	0.00%	19 Missing ⚠️
...kotlin/radio/ks3ckc/ft8us/ui/components/TxStrip.kt	0.00%	18 Missing ⚠️
...om/bg7yoz/ft8cn/ft8listener/FT8SignalListener.java	0.00%	13 Missing ⚠️
...om/bg7yoz/ft8cn/ft8transmit/FT8TransmitSignal.java	0.00%	13 Missing ⚠️
...java/com/bg7yoz/ft8cn/ft8transmit/GenerateFT8.java	0.00%	10 Missing ⚠️
...in/java/com/bg7yoz/ft8cn/database/DatabaseOpr.java	0.00%	9 Missing ⚠️
.../java/com/bg7yoz/ft8cn/database/OperationBand.java	50.00%	5 Missing and 3 partials ⚠️
...n/radio/ks3ckc/ft8us/ui/components/SlotTimerBar.kt	0.00%	6 Missing ⚠️
...pp/src/main/java/com/bg7yoz/ft8cn/ModeProfile.java	83.33%	4 Missing ⚠️
... and 3 more

Additional details and impacted files

@@            Coverage Diff             @@
##               dev    #163      +/-   ##
==========================================
+ Coverage     6.53%   6.58%   +0.05%     
- Complexity     682     695      +13     
==========================================
  Files          269     271       +2     
  Lines        31113   31412     +299     
  Branches      4897    4959      +62     
==========================================
+ Hits          2032    2070      +38     
- Misses       28939   29198     +259     
- Partials       142     144       +2     

Files with missing lines	Coverage Δ
...c/main/java/com/bg7yoz/ft8cn/GeneralVariables.java	34.83% <100.00%> (+0.62%)	⬆️
...src/main/java/com/bg7yoz/ft8cn/timer/UtcTimer.java	26.37% <100.00%> (+0.81%)	⬆️
...adio/ks3ckc/ft8us/pskreporter/PskReporterClient.kt	70.94% <100.00%> (+0.25%)	⬆️
...n/kotlin/radio/ks3ckc/ft8us/ComposeMainActivity.kt	0.00% <0.00%> (ø)
...in/kotlin/radio/ks3ckc/ft8us/ui/pota/PotaScreen.kt	0.00% <0.00%> (ø)
...ks3ckc/ft8us/ui/components/FrequencyPickerSheet.kt	0.00% <0.00%> (ø)
...pp/src/main/java/com/bg7yoz/ft8cn/ModeProfile.java	83.33% <83.33%> (ø)
...n/radio/ks3ckc/ft8us/ui/components/SlotTimerBar.kt	0.00% <0.00%> (ø)
.../java/com/bg7yoz/ft8cn/database/OperationBand.java	55.17% <50.00%> (-1.00%)	⬇️
...in/java/com/bg7yoz/ft8cn/database/DatabaseOpr.java	0.00% <0.00%> (ø)
... and 6 more

... and 1 file with indirect coverage changes

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[Copilot]

Pull request overview

Adds FT4 as a first-class operating mode alongside FT8, refactoring timing/encoding/UI and band dial selection around a new ModeProfile descriptor so additional modes can be added with minimal churn.

Changes:

• Introduces ModeProfile and threads mode-aware timing/slot length through RX/TX timers, UI slot bar, and logging/spotting strings.
• Adds FT4 band dials and mode-aware band parsing/filtering so pickers show the correct per-mode frequencies.
• Adds a native JNI shim to expose FT4 encoding via the prebuilt libft8cn.so and links it into the CMake-built libft8af_usb.so.

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
ft8cn/app/src/test/java/com/bg7yoz/ft8cn/timer/UtcTimerTest.java	Adds slot-length-aware sequential timer tests (FT8/FT4).
ft8cn/app/src/test/java/com/bg7yoz/ft8cn/ModeProfileTest.java	New pure-logic tests validating ModeProfile descriptors and id resolution.
ft8cn/app/src/test/java/com/bg7yoz/ft8cn/database/OperationBandTest.java	Extends band parsing tests for FT4-tagged entries and mode dial lookup.
ft8cn/app/src/main/res/values/strings_compose.xml	Adds user-visible strings for mode switch toasts.
ft8cn/app/src/main/kotlin/radio/ks3ckc/ft8us/ui/pota/PotaScreen.kt	Uses current mode display name for POTA spot mode field.
ft8cn/app/src/main/kotlin/radio/ks3ckc/ft8us/ui/components/TxStrip.kt	Adds a mode “pill” UI control to cycle modes (disabled while TX).
ft8cn/app/src/main/kotlin/radio/ks3ckc/ft8us/ui/components/SlotTimerBar.kt	Parameterizes slot length (15s/7.5s) for progress/countdown rendering.
ft8cn/app/src/main/kotlin/radio/ks3ckc/ft8us/ui/components/FrequencyPickerSheet.kt	Filters frequency picker entries by operating mode and recomposes on mode changes.
ft8cn/app/src/main/kotlin/radio/ks3ckc/ft8us/pskreporter/PskReporterClient.kt	Uses current mode display name in PSKReporter queries.
ft8cn/app/src/main/kotlin/radio/ks3ckc/ft8us/FT8USApp.kt	Wires mode state into UI (mode pill + slot bar) and calls setOperatingMode.
ft8cn/app/src/main/java/com/bg7yoz/ft8cn/timer/UtcTimer.java	Adds sequential(utc, slotMillis) and makes default sequential mode-aware.
ft8cn/app/src/main/java/com/bg7yoz/ft8cn/ModeProfile.java	New descriptor table for per-mode timing/symbol/encode dispatch.
ft8cn/app/src/main/java/com/bg7yoz/ft8cn/MainViewModel.java	Adds mode LiveData and setOperatingMode (persist + rebuild timers + in-band retune).
ft8cn/app/src/main/java/com/bg7yoz/ft8cn/GeneralVariables.java	Adds operatingMode global and currentMode() helper.
ft8cn/app/src/main/java/com/bg7yoz/ft8cn/ft8transmit/GenerateFT8.java	Generalizes tone/audio synthesis per mode; adds FT4 encode JNI method.
ft8cn/app/src/main/java/com/bg7yoz/ft8cn/ft8transmit/FT8TransmitSignal.java	Makes TX timer/mode timing mode-aware; rebuilds timer on mode switch.
ft8cn/app/src/main/java/com/bg7yoz/ft8cn/ft8listener/FT8SignalListener.java	Makes RX timer/recording window/decoder init mode-aware; supports timer rebuild.
ft8cn/app/src/main/java/com/bg7yoz/ft8cn/database/OperationBand.java	Adds mode-tagged band parsing and mode-specific dial lookup; filters visible bands by mode.
ft8cn/app/src/main/java/com/bg7yoz/ft8cn/database/DatabaseOpr.java	Persists mode string in SWL logs; loads operatingMode from config.
ft8cn/app/src/main/cpp/ft4_encode_jni.cpp	New JNI bridge exposing ft4_encode from the prebuilt DSP library.
ft8cn/app/src/main/cpp/CMakeLists.txt	Links ft8af_usb against imported prebuilt libft8cn.so for FT4 encode shim.
ft8cn/app/src/main/assets/bands.txt	Adds FT4 dial entries tagged with :FT4.

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