Replace sidebar + 5-screen layout with horizontal tab bar (F1-F4)
and persistent StatusStrip. Consolidate Position + Scan screens into
Signal (F3) with Monitor/Sweep/Sky Map sub-modes via ModeBar.
Screens:
- F1 Dashboard: system health, tracking panel, quick actions, presets
- F2 Control: motor tuning, compass rose, preset management
- F3 Signal: RSSI monitor, 1D sweep (SweepPlot), 2D sky map (heatmap)
- F4 System: NVS editor with regex filter, EEPROM, firmware info
- F5 Console: push/pop overlay (no longer a tab)
New widgets: StatusStrip, ModeBar, SweepPlot, QuickActions, PresetList,
ReceiverInfo, MotorTuning, NvsFilter, SystemHealth, TrackingPanel.
Removed: PositionScreen, ScanScreen, DeviceStatusBar (functionality
absorbed into new screens and StatusStrip).
App-level position poll feeds StatusStrip and active screen at ~2 Hz.
Fix shared threading.Event across instances (class-level mutable default).
Stop handler now calls cancel_operation() on the device bridge,
which sets a threading.Event that interrupts the 2s-timeout serial
read loop in send_with_timeout(). InterruptedError is caught
separately to prevent falling back to software sweep on cancel.
disconnect() uses acquire(timeout=5) with force-close fallback
instead of blocking lock acquisition — prevents deadlock when a
stuck worker holds the serial lock during shutdown.
Add 3 Textual async tests (pytest-asyncio) to verify Stop behavior:
firmware sweep stop, software sweep stop, and sweep restart.
