feat: Add --all flag to bd list for CLI familiarity

Common CLI pattern (git branch -a, docker ps -a, ls -a).
No-op since bd list already shows all issues by default,
but prevents error/retry cycles when agents reflexively use it.

cmd/bd/list.go

@@ -210,6 +210,7 @@ func init() {
 	listCmd.Flags().String("id", "", "Filter by specific issue IDs (comma-separated, e.g., bd-1,bd-5,bd-10)")
 	listCmd.Flags().IntP("limit", "n", 0, "Limit results")
 	listCmd.Flags().String("format", "", "Output format: 'digraph' (for golang.org/x/tools/cmd/digraph), 'dot' (Graphviz), or Go template")
+	listCmd.Flags().Bool("all", false, "Show all issues (default behavior; flag provided for CLI familiarity)")
 	rootCmd.AddCommand(listCmd)
 }