feat(ui): offer a cube navigator alongside signed axes (#664)

Adds a View navigator preference (Navigation page) with an optional cube navigator alongside the signed axes, which stay the default (#165).

crates/engine/src/cmd/mod.rs

@@ -53,6 +53,7 @@ mod sketch_modify;
 mod sketch_project;
 mod surface;
 mod surface_analysis;
+mod view_navigation;
 
 use serde::Serialize;
 use serde_json::Value;
@@ -219,6 +220,7 @@ pub fn command_specs() -> Vec<&'static CommandSpec> {
     v.extend(inspect::COMMANDS.iter());
     v.extend(materials::COMMANDS.iter());
     v.extend(section::COMMANDS.iter());
+    v.extend(view_navigation::COMMANDS.iter());
     v.extend(diagnostics::COMMANDS.iter());
     v
 }