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

crates/doc/src/project.rs

@@ -485,7 +485,7 @@ fn tilted_circle(plane: &Plane, pts: &[Vec3]) -> Option<Vec<LinkGeom>> {
     let (c, n, r, closed) = circle3(pts)?;
     let sn = plane.normal();
     let cosang = n.dot(sn).abs();
-    if cosang > 1.0 - 1e-12 || cosang < 1e-9 {
+    if !(1e-9..=1.0 - 1e-12).contains(&cosang) {
         return None;
     }
     if closed {