Handle Provider-ID mismatch after repository rename #134
Description
When a repository is renamed (e.g., git-issue → git-native-issue), issues imported under the old name carry Provider-ID trailers like github:owner/old-name#N. The export logic treats these as foreign (imported from a different repo) and skips them during sync.
This means state changes and new comments on those issues won't be pushed back to GitHub.
Affected: 25 issues imported from github:remenoscodes/git-issue before the rename to git-native-issue.
Possible approaches:
- Teach export to recognize provider aliases/redirects (config-based)
- Add a migration command to rewrite Provider-ID trailers
- Accept GitHub's redirect and match on owner/issue-number ignoring repo name
Needs careful design — Provider-ID immutability is a feature (commit integrity), so any fix should preserve that property.