Follow-up to the #4420 opener hardening: absolute-path rundll32 fixes the
stripped-PATH spawn throw, but rundll32 exits 0 unconditionally, so the
delayed-failure telemetry added there can never observe a Windows launch
failure. Replace it with %SystemRoot%-resolved PowerShell Start-Process
via -EncodedCommand:
- failures ShellExecute itself reports (missing target, no handler
executable, access denied) surface as exit code 1 and reach the
existing non-zero-exit logging (verified live on Windows 11: missing
file exits 1; unregistered schemes exit 0 on any opener because the
OS hands them to the app-picker — documented limitation);
- the UTF-16LE/base64 payload keeps OAuth query strings opaque to
cmd/PowerShell metacharacter parsing; embedded single quotes are
doubled into a PS literal;
- %SystemRoot% anchoring with a bare-name PATH fallback preserves the
stripped-PATH resilience from #4420.
Also pins the WSL-mount test's path.resolve against Windows dev hosts
so the mocked linux platform stays deterministic.
Refs #4418