Bare clones don't have remote.origin.fetch set by default, which breaks
worktrees that need to fetch and see origin/* refs. This caused refinery
to fail because origin/main never appeared after fetch.
- Add configureRefspec() to set standard refspec on bare repos
- Call from CloneBare() and CloneBareWithReference()
- Add BareRepoRefspecCheck to doctor for existing rigs
Closes#286
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>