[jonschwenk]

Summary

• write start_year and end_year as one-element i4 variables on a scalar dimension in every met NetCDF, matching the flexible-date format read by ELM
• default met filenames to <DRIVER>_<VAR>_<START>-<END>_z01.nc using the actual exported year range
• preserve explicit {var} filename templates and legacy simple-prefix overrides
• update the Toolik workflow and user documentation

Context

E3SM PR NGEE-Arctic/E3SM#25 reads start_year and end_year variables for Daymet, while the ERA5 path still hardcodes its date range. This PR supplies that same machine-readable contract on the Dapper side while retaining the established year range and zone suffix in filenames. Follow-up E3SM work in NGEE-Arctic/E3SM#5 can consume these variables for ERA5.

Verification

• 47 passed, 1 skipped
• smoke export inspected with ncdump: scalar = 1, int start_year(scalar), and int end_year(scalar) with values matching the filename
• Sphinx HTML build succeeded with three existing warnings