feat: implement --state filter for issue list command
Add support for filtering issues by state (open/closed) using the
--state flag on `tangled issue list`.
Implementation:
- Add list_issue_states() API method to fetch state records
- Add IssueState struct for sh.tangled.repo.issue.state records
- Filter issues client-side by fetching state records and matching
- Default to "open" state for issues without explicit state records
💖 Generated with Crush
Assisted-by: Claude Sonnet 4.5 via Crush <crush@charm.land>