Add nil check at start of ResolvePartialID to return a proper error
instead of panicking when storage interface is nil.
Root cause: When bd refile (or other commands) is called with a nil
storage, calling store.SearchIssues() panics with SIGSEGV. This can
happen when routing fails to initialize storage properly.
Now returns: "cannot resolve issue ID <id>: storage is nil"
Fixes: bd-7ypor
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>