chore: clippy send + sync warnings, drop warnings

src/command/cmd.rs

@@ -38,7 +38,7 @@ pub struct CmdContext<'a> {
 }
 
 /// A command that reads state and produces effects.
-pub trait Cmd: Debug {
+pub trait Cmd: Debug + Send + Sync {
     fn execute(&self, ctx: &CmdContext) -> Vec<Box<dyn Effect>>;
     fn name(&self) -> &str;
 }