Add the exhaustive-match error code to the mypy configuration. This
requires all match statements to be exhaustive, handling all possible
values of the matched expression.
The fix is to add 'case _: pass' to each match statement that is
intended to be non-exhaustive, making the non-exhaustiveness explicit.
Assisted-by: unsloth/Qwen3.6-35B-A3B-GGUF:IQ4_NL and pi.dev 0.81.1
Signed-off-by: Jan Lindemann <jan@janware.com>