Implements bd-235: New reopen command makes reopening issues more explicit than 'bd update --status open'. Features: - Sets status to 'open' and automatically clears closed_at - Emits EventReopened via UpdateIssue - Optional --reason flag to add comment - JSON output support - Auto-flush after operation Closes: bd-234, bd-235, bd-236, bd-237, bd-238, bd-239 Related: bd-224 (status/closed_at invariant enforcement) Amp-Thread-ID: https://ampcode.com/threads/T-b1c82629-3521-440f-9f16-ab6d66fb5091 Co-authored-by: Amp <amp@ampcode.com>