Web app: 3D mouse navigation through the Gamepad API (#1473)

The web app reads a 3D mouse through the Gamepad API and drives the camera through navigation::device, so it follows each page's navigation capabilities (#1336).

Co-authored-by: CamWight <CamWight@users.noreply.github.com>
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

apps/solidcraft-web/src/main.rs

@@ -10,6 +10,8 @@
 mod files;
 #[cfg(target_arch = "wasm32")]
 mod install;
+#[cfg(any(target_arch = "wasm32", test))]
+mod space_mouse;
 
 #[cfg(target_arch = "wasm32")]
 mod web {
@@ -21,6 +23,7 @@ mod web {
     use wasm_bindgen::JsCast as _;
 
     use crate::files::{self, Files, Intent};
+    use crate::space_mouse::SpaceMouse;
 
     const CANVAS_ID: &str = "solidcraft_canvas";
     const LOADING_ID: &str = "solidcraft_loading";
@@ -67,6 +70,7 @@ mod web {
         /// On-demand CJK font: fetched only when a CJK language is selected.
         font: solidcraft_ui_egui::fonts::CjkFontLoader,
         font_result: FontLoadResult,
+        space_mouse: SpaceMouse,
     }
 
     impl Shell {
@@ -382,11 +386,14 @@ mod web {
         fn logic(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
             self.tick_font(ctx);
             self.app.logic(ctx);
+            self.space_mouse.logic(&mut self.app, ctx);
             self.files_tick(ctx);
             UNSAVED.with(|u| u.set(solidcraft_ui_egui::documents::any_dirty(&self.app)));
         }
-        fn raw_input_hook(&mut self, _ctx: &egui::Context, raw: &mut egui::RawInput) {
+        fn raw_input_hook(&mut self, ctx: &egui::Context, raw: &mut egui::RawInput) {
             files::take_drops(&self.files, raw);
+            // Before the app's own hook, which adds the control channel's events.
+            self.space_mouse.raw_input_hook(ctx, self.app.preferences.space_mouse_enabled, raw);
             self.app.raw_input_hook(raw);
         }
         fn ui(&mut self, ui: &mut egui::Ui, _frame: &mut eframe::Frame) {
@@ -516,6 +523,7 @@ mod web {
                             recents_synced: false,
                             font: Default::default(),
                             font_result: Rc::new(std::cell::RefCell::new(None)),
+                            space_mouse: SpaceMouse::default(),
                         }))
                     }),
                 )