agent: Staff ship subagents (#49885)

Release Notes:

- N/A

crates/feature_flags/src/flags.rs

@@ -43,7 +43,7 @@ impl FeatureFlag for SubagentsFeatureFlag {
     const NAME: &'static str = "subagents";
 
     fn enabled_for_staff() -> bool {
-        false
+        true
     }
 }