Camera backend abstraction wrapping fswebcam/ffmpeg/libcamera-still via
subprocess, with DemoCamera fallback generating valid JPEG from raw bytes.
Capture pipeline writes JPEG + JSON sidecar always, optional FITS (astropy)
and EXIF (Pillow) when available. Thread-safe orchestrator with session
tracking, sequence numbering, and date-based output directories.
Trigger system: manual capture, configurable interval timer, and pass event
detection (AOS/TCA/LOS) with 0.5-degree TCA hysteresis. PassEventDetector
runs in the Craft tracking loop, fires callbacks to the camera overlay.
F6 overlay follows the F5 ConsoleOverlay pattern — ModalScreen with
install_screen persistence. Status panel, scrollable capture log, interval
controls, and AOS/TCA/LOS toggle buttons.
Tagline: "a generic AZ/EL positioner that doesn't care about wavelength"
added to TUI header subtitle.
51 new tests (77 total passing).
