Add a typed facade for the tracking camera over the camera_interface module

[mikelangmayr]

• camera_interface exposes instrument commands as instrument_cmd(name, argument_string), so every caller would otherwise build the same argument strings by hand; TrackingCamera gives them real signatures and puts the formatting in one place
• set_guiding_roi(y0, y1, x0, x1), set_centred_roi(height, width), set_readmode(ReadMode.RX), set_window(bool), set_autofetch(bool), set_freerun(bool), and initialize() for the open, load, power on, h2rg_init sequence
• geometry() returns a Geometry dataclass with height and width rather than a string to parse, and ReadMode is an enum so a bad mode raises ValueError before anything is sent
• anything not defined here forwards to the underlying camera_interface.Camera, so base commands like expose and exptime are reached directly without re-wrapping all 22
• pure Python over the existing bindings, so nothing in camerad changes and no camera behaviour is at risk
• 9 unit tests run against a fake camera, needing neither the compiled extension nor hardware; also exercised end to end against the Archon emulator, including a guiding ROI reading back as 10x10 and an exposure writing FITS
• driver README covers the one unusual prerequisite, that camera_interface is a compiled extension rather than a PyPI package

[prkrtg]

Should we update the toml to install this?

[mikelangmayr]

No: pybind11 is only needed to compile camera_interface, not to import it (the built .so links cfitsio, CCfits and OpenCV but not pybind11), so it is camera-interface's build dependency rather than one of ours, and camera_interface itself cannot go in the toml either since it is a compiled extension built per instrument rather than a package on an index. The real fix is to package camera-interface with scikit-build-core so pip install ./camera-interface --config-settings=cmake.define.INSTRUMENT=... pulls pybind11 into an isolated build env and installs the module into the venv, which deletes this instruction instead of explaining it; that is planned as a separate piece of work. README now says build-only.