Replace broken control characters and U+FFFD replacement characters in
log function labels with ASCII equivalents ([ok], [!], [x]).
Drop the hardcoded "main" default for git_ref so arty deps no longer
fails with "pathspec 'main' did not match" on repos whose default branch
is not named main — git clone already checks out the remote default branch.
A ref: value in arty.yml is still honoured when explicitly set.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
valknar