Auto git-push on `tsk reject` and default origin for git-push/git-pull
Reject mirrors assign: pushes refs to "origin" by default after writing
the rejection event into the source's log. `-r NAME` selects a different
remote; `-r ""` skips.
`tsk git-push` and `tsk git-pull` now treat the remote argument as
optional, defaulting to "origin" when configured. Errors out when no
remote is supplied and no origin is set.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>