fix: restore Windows build under wmi 0.18 API

wmi 0.18 removed `COMLibrary` (COM now initialises automatically per
thread) and changed `WMIConnection::with_namespace_path` to take only the
namespace path. Update the two doctor WMI checks to the new API; the rest
of the Windows code already used it.

Also resolve the two Windows-only warnings this surfaced: gate
`Duration`/`try_exec` imports in doctor/bundle.rs to `unix` (their only
consumers), and silence the unused `config` parameter in
`AllSmi::with_config` on platforms without platform-specific init.