metno/pysurfex — reverse-engineered prompt

Build me a Python package and command line tool for working with the SURFEX surface model. I want it to help prepare the input files and namelists needed to run an existing SURFEX binary, create atmospheric forcing for offline runs, read the model output, and make simple plots of results. It should work with common weather data formats like NetCDF, GRIB, and FA when the needed libraries are installed.

Also include tools for handling observations, doing basic quality control, running optimal interpolation when optional libraries are available, and showing how observations were used. Please make it installable with pip, usable from scripts, and usable from terminal commands. Add examples, tests, and clear docs so a scientist can set up an environment, run a small example, and understand what files are produced.