fix(commands): distinguish empty query results

Track exit codes that indicate an empty package query separately from
accepted success codes.

Treat pacman exit status 1 as an empty result only when both stdout and
stderr are empty, while preserving genuine command failures as errors.

Apply the empty-result handling to pacman queries that may legitimately
return no packages, including update checks.

0 files changed, 0 insertions, 0 deletions