Fix viewport input leaking through dialogs

Use egui pointer ownership for viewport navigation and picking, view-cube
interaction, and sketch-dimension hover. Cover scrolling, model selection,
and cube interaction under floating dialogs, including after they close.
Shield constraint glyph and move-gizmo highlights from overlapping UI too.

Clear strict Clippy warnings and use the same saved path in the recent-file
scenario on Windows and Unix.

Fixes #87

xtask/src/layers.rs

@@ -163,11 +163,10 @@ pub fn check(crates: &[Crate]) -> Vec<Violation> {
                 match classify(&d.name) {
                     // Unregistered deps are reported on their own entry.
                     None => {}
-                    Some(Class::Testkit) => {
-                        if d.kind != DepKind::Dev {
-                            out.push(Violation::TestkitAsNormalDep { krate: c.name.clone() });
-                        }
+                    Some(Class::Testkit) if d.kind != DepKind::Dev => {
+                        out.push(Violation::TestkitAsNormalDep { krate: c.name.clone() });
                     }
+                    Some(Class::Testkit) => {}
                     Some(dc) => {
                         let to = dc.layer().unwrap_or(u8::MAX);
                         if to >= layer && !(to == layer && intra_layer_allowed(&c.name, &d.name)) {