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/sketch/src/model.rs

@@ -698,10 +698,8 @@ impl Sketch {
             | Symmetric { l, .. }
             | PointLineDistance { l, .. }
             | LinearDiameter { l, .. } => need_line(l)?,
-            ArcLength { c, .. } => {
-                if !matches!(self.curves.get(c).map(|c| &c.kind), Some(CurveKind::Arc { .. })) {
-                    return Err(SketchError::WrongKind(name(c), "arc length needs an arc".into()));
-                }
+            ArcLength { c, .. } if !matches!(self.curves.get(c).map(|c| &c.kind), Some(CurveKind::Arc { .. })) => {
+                return Err(SketchError::WrongKind(name(c), "arc length needs an arc".into()));
             }
             Smooth { a, b } => {
                 let ends = |i: usize| self.curves.get(i).and_then(|c| c.kind.ends());
@@ -730,10 +728,8 @@ impl Sketch {
                     return Err(SketchError::WrongKind(name(a), "tangent needs a circle or arc".into()));
                 }
             }
-            Equal { a, b } => {
-                if is_line(a) != is_line(b) {
-                    return Err(SketchError::WrongKind(name(b), "equal needs two lines or two circles/arcs".into()));
-                }
+            Equal { a, b } if is_line(a) != is_line(b) => {
+                return Err(SketchError::WrongKind(name(b), "equal needs two lines or two circles/arcs".into()));
             }
             Coincident { p, q } if p == q => return Err(SketchError::Invalid("a point is always coincident with itself".into())),
             _ => {}

crates/sketch/src/text.rs

@@ -74,7 +74,7 @@ pub fn text_geometry(text: &str, at: Vec2, height: f64, angle: f64) -> Result<Ve
     if text.chars().count() > MAX_TEXT_CHARS {
         return Err(SketchError::TooLarge);
     }
-    if !(height.is_finite() && height > 1e-6 && height < 1e6) || !angle.is_finite() || !at.is_finite() {
+    if !(height.is_finite() && height > 1e-6 && height < 1e6 && angle.is_finite() && at.is_finite()) {
         return Err(SketchError::Invalid("text height must be positive".into()));
     }
     let face = ttf_parser::Face::parse(FONT, 0).map_err(|e| SketchError::Invalid(format!("font: {e}")))?;