Flat pattern gets its own pan and zoom through the shared navigation (#1484)

The flat pattern now keeps a 2D view of its own, driven by navigation::handle with orbit off,
so pan, zoom to the cursor and reverse zoom follow the navigation preset. Input over it no
longer reaches the Design camera, and Fit and Home frame the pattern. Closes #1483.

crates/ui-egui/src/viewport.rs

@@ -2100,6 +2100,12 @@ pub fn show(app: &mut SolveApp, ui: &mut egui::Ui) {
     app.viewport.rect = Some(rect);
     refresh_layout(app, ui.ctx().pixels_per_point());
     let resp = ui.interact(rect, ui.id().with("viewport"), Sense::click_and_drag());
+    let flat = crate::dialogs_sheet::flat_active(app);
+    if !flat {
+        app.flat_view.fitted = false;
+    }
+    let input =
+        if flat { crate::dialogs_sheet::navigate(app, ui, rect, &resp) } else { crate::navigation::handle(app, ui, rect, &resp, NavCaps::MODEL) };
     let CameraInput {
         hover,
         scroll,
@@ -2115,7 +2121,7 @@ pub fn show(app: &mut SolveApp, ui: &mut egui::Ui) {
         pan,
         primary_nav,
         mode,
-    } = crate::navigation::handle(app, ui, rect, &resp, NavCaps::MODEL);
+    } = input;
     app.viewport.physical_scale = ui.ctx().pixels_per_point();
     let proj = projection(app, rect);
     if let Ok(mut cache) = app.viewport.display.lock() {