feat(cli): don't require executor arg anymore

crates/executor/src/lib.rs

@@ -7,13 +7,9 @@ mod value;
 /// The available executors
 /// unused in early dev.
 #[derive(Debug, Clone, Copy, clap::ValueEnum)]
-pub enum Executors {
+pub enum RegisteredExecutor {
     /// the debug executor is single threaded and really, *really* slow. And unstable. Don't use. Unless you're a dev working on this.
     Debug,
-    /// the CPU executor primarily uses the CPU. Most likely most feature complete, and the fallback.
-    Cpu,
-    /// the Vulkan executor (obviously) uses vulkan. there's a good chance this isn't implemented yet as you're reading this.
-    Vulkan,
 }
 
 trait Executor {