Add 'case _: pass' to match statements that are intentionally
non-exhaustive, satisfying the new exhaustive-match mypy rule.
Also replaced 'case '_':' (a string literal) with 'case _: pass' in
pkg_relations.py since it was an unreachable case (syntax is a
VersionSyntax enum, not a str).
Added 'case VersionSyntax.names_only:' to the match in pkg_relations.py
to handle the missing enum value.
Files modified:
- util.py: Two match statements for askpass env vars
- Distro.py: Three match statements for backend/os detection
- pkg_relations.py: Match on VersionSyntax enum
- CmdListRepos.py: Match on URL scheme
Assisted-by: unsloth/Qwen3.6-35B-A3B-GGUF:IQ4_NL and pi.dev 0.81.1
Signed-off-by: Jan Lindemann <jan@janware.com>