Raise pylint score from 7.29 to 10.00/10

- Fix 17x no-else-return across comparison and math operators, system
  property, unit property, from_other, and best_prefix
- Refactor best_prefix: extract nested _resolve_prefix_table helper to
  bring branch count under threshold; simplify index logic; use f-strings
- Add real docstrings to all 32 leaf unit subclasses and 34 to_* methods
- Add real docstrings to DISK_GEOMETRY / DISK_GEOMETRY_EX ctypes structs
- Convert 2 orphaned bare string statements to # comments
- Rename local ord -> result in __or__ to avoid shadowing builtin
- Surgical inline pylint: disable comments for intentional API names
  (bytes parameter, sum/format functions) and platform-guarded imports
- pyproject.toml: good-names-rgxs for unit naming conventions (kB, kb,
  to_KiB, etc.), max-module-lines raised to 2000

Author: timlnx