Render preview uses the shared camera navigation (#1462)

* Render preview uses the shared camera navigation

The Render workspace's product preview had its own hard-coded camera
controls. Camera input now lives in one component, navigation::handle,
which the modelling viewport and the Render preview both call (NavCaps:
orbit, pick). Render gets the navigation preset, Orbit around, zoom to the
cursor, the middle double-click and the axis view or navigation cube.
Flat pages can call it with orbit off. A test rejects pages that read the
wheel or move the camera themselves.

Fixes #1454

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Render panel hint says the camera moves as in Design

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/ui-egui/src/prefs.rs

@@ -604,44 +604,6 @@ pub fn zoom_sign(app: &SolveApp) -> f64 {
     if app.preferences.zoom_reverse { -1.0 } else { 1.0 }
 }
 
-/// Orbit by pixel deltas about the configured centre: the view's centre (default), the world
-/// origin, or the model point that was under the cursor when the drag began. The origin and the
-/// cursor pivot are kept still on screen; a cursor drag that begins over empty space turns around
-/// the centre of the visible geometry instead, so the model never swings around a far-off point.
-/// The cursor pivot is chosen once, when the drag begins.
-pub fn orbit(app: &mut SolveApp, rect: egui::Rect, dx: f64, dy: f64, press: Option<Pos2>) {
-    let pivot = match app.preferences.orbit_around {
-        OrbitAround::ViewCentre => None,
-        OrbitAround::Origin => Some(Vec3::ZERO),
-        OrbitAround::Cursor => Some(match app.viewport.orbit_pivot {
-            Some(p) => p,
-            None => {
-                let proj = crate::viewport::projection(app, rect);
-                let at = press.unwrap_or(rect.center());
-                let p = pivot_under(app, &proj, at);
-                app.viewport.orbit_pivot = Some(p);
-                p
-            }
-        }),
-    };
-    let Some(pivot) = pivot else {
-        app.cam.orbit(dx, dy);
-        return;
-    };
-    orbit_about(app, rect, dx, dy, pivot);
-}
-
-/// Orbit by pixel deltas, keeping `pivot` still on screen: the camera turns about it and a pan
-/// correction puts it back where it was.
-fn orbit_about(app: &mut SolveApp, rect: egui::Rect, dx: f64, dy: f64, pivot: Vec3) {
-    let before = crate::viewport::projection(app, rect).to_screen(pivot);
-    app.cam.orbit(dx, dy);
-    let after = crate::viewport::projection(app, rect).to_screen(pivot);
-    if let (Some(a), Some(b)) = (before, after) {
-        app.cam.pan(f64::from(a.x - b.x), f64::from(a.y - b.y), f64::from(rect.height().max(1.0)));
-    }
-}
-
 /// The model point under a screen position. Over empty space: the centre of the visible bodies
 /// and sketches (what Fit frames), or the view's centre when nothing is visible.
 pub(crate) fn pivot_under(app: &SolveApp, proj: &crate::viewport::Proj, at: Pos2) -> Vec3 {
@@ -1521,6 +1483,7 @@ mod tests {
     }
 
     use super::*;
+    use crate::navigation::orbit;
 
     #[test]
     fn unsupported_saved_msaa_is_reset_to_the_default_with_a_notice() {