topology: unify CLI and types::Topology (ValueEnum + aliases); bcachefs-2copy uses --replicas=2; update orchestrator call to make_filesystems(cfg); minor overlay fix; docs previously synced

src/config/loader.rs

@@ -271,8 +271,8 @@ fn cli_overlay_value(cli: &Cli) -> Value {
         root.insert("device_selection".into(), Value::Object(device_selection));
     }
 
-    // topology override via --topology
-    if let Some(t) = cli.topology {
+    // topology override via --topology (avoid moving out of borrowed field)
+    if let Some(t) = cli.topology.as_ref() {
         root.insert("topology".into(), Value::String(t.to_string()));
     }