Sync panadapter RX antenna status

[rfoust]

Summary:

• track panadapter rxant status and drive overlay antenna selection from radio echo
• send overlay RX antenna changes with display pan set, matching FlexLib panadapter behavior
• keep overlay RF gain panadapter-authoritative and cover rxant/rfgain status in a focused test

Verification:

• cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=RelWithDebInfo
• cmake --build build -j8
• ctest --test-dir build -R panadapter_model_rx_antenna_test --output-on-failure

[Copilot]

Pull request overview

This PR makes panadapter RX antenna state radio-authoritative and routes overlay antenna changes through display pan set, aligning overlay behavior with panadapter-level status echoes.

Changes:

• Adds rxAntenna state/signaling to PanadapterModel.
• Updates SpectrumOverlayMenu to track the owning panadapter, prefer panadapter antenna/RF gain state, and send RX antenna changes as pan commands.
• Adds a focused CTest covering panadapter rxant and rfgain status change behavior.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/models/PanadapterModel.h	Adds RX antenna accessor, signal, and backing state.
src/models/PanadapterModel.cpp	Parses rxant from pan status and emits changes.
src/gui/SpectrumOverlayMenu.h	Adds panadapter tracking and helper declarations.
src/gui/SpectrumOverlayMenu.cpp	Routes overlay RX antenna selection via pan commands and syncs from panadapter state.
tests/panadapter_model_rx_antenna_test.cpp	Adds regression coverage for rxant and rfgain status updates.
CMakeLists.txt	Registers the new panadapter model test target with CTest.

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[aethersdr-agent]

Thanks @rfoust — this looks good. The design mirrors how wnb/rfgain are already handled (panadapter-authoritative, with display pan set <panId> rxant=), and the new rxAntenna field in PanadapterModel::applyPanStatus follows the same dedup-then-emit pattern as the surrounding keys.

A few small things worth confirming, none blocking:

• Slice fallback path in the combo handler is effectively dead. With setPanId() and setRadioModel() always called before setSlice() in MainWindow::buildPanadapter, the else if (m_slice) branch in SpectrumOverlayMenu.cpp:319 only runs during early construction. That's fine and matches the stated intent ("send overlay RX antenna changes with display pan set"), but it means VFO-widget RxAntenna and the overlay combo now diverge in transport — the overlay always targets the pan, VfoWidget/RxApplet still target the slice. Worth a sanity check that this doesn't cause the panadapter overlay combo to drift out of sync with VFO-side selections in a multi-slice pan when the user only touches one path.

• Implicit ordering dependency. setPanId() and setRadioModel() both call wirePanadapterRxAntenna(), and it only does anything once both have run — which works today because of the MainWindow call order at src/gui/MainWindow.cpp:10348-10350. Not a bug, just a latent constraint if anyone reorders those calls later. A short comment on wirePanadapterRxAntenna() noting "no-op until both panId and radioModel are set" would save a future reader.

• The QPointer<PanadapterModel> m_panadapter plus reset in setRadioModel(nullptr) correctly guards against RadioModel teardown — nice.

Test coverage is appropriately focused (rxant set/dedup/change + rfgain dedup). LGTM.