M3.76: Attributes panel with overprint, centre point, path direction, fill rule, image map, URL and note

Window > Attributes (Cmd+F11) shows Overprint Fill/Stroke, Show/Don't Show
Center, Reverse Path Direction Off/On, the non-zero / even-odd fill rule,
Image Map, a URL field with recent URLs and a Browser button, and a note.
New commands attributes.set and path.setFillRule; path.reverse takes ids and
reversed; attributes.info reports every value. Objects keep the attributes in
Node.attrs. SVG export wraps linked objects in <a>, and import reads links
back. The canvas draws the centre point of selected objects that show it.

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

crates/engine/src/lib.rs

@@ -507,6 +507,8 @@ pub struct Session {
     pub(crate) freeform_point: Option<(usize, cmd::gradient::StopOwner)>,
     /// User Defined and loaded graphic style libraries (Window → Graphic Style Libraries); not saved.
     pub style_libraries: cmd::stylelib::Libraries,
+    /// URLs recently given in the Attributes panel (`attributes.set {url}`), newest first; not saved.
+    pub recent_urls: Vec<String>,
 }
 
 impl Default for Session {
@@ -541,6 +543,7 @@ impl Session {
             swatch_libraries: Default::default(),
             freeform_point: None,
             style_libraries: Default::default(),
+            recent_urls: vec![],
         }
     }
 
@@ -787,6 +790,8 @@ mod tests;
 #[cfg(test)]
 mod tests_appearance;
 #[cfg(test)]
+mod tests_attributes;
+#[cfg(test)]
 mod tests_brushsym;
 #[cfg(test)]
 mod tests_build;