Add pin.go and unpin.go to cmd/bd/ for managing pinned issues.
- bd pin <id> sets Pinned=true on an issue
- bd unpin <id> sets Pinned=false on an issue
Also adds Pinned field support to RPC UpdateArgs for daemon mode.
🤝 Slit
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>