Tools: readouts measure in the document's ruler units

Tool readouts (the Page tool's size while dragging, smart-guide distances, the
resize readout) took their unit from the UI's own setting, which nothing changes
from picas, so a document set to inches read in picas. The tool context now takes
the active document's horizontal ruler unit, and the Page tool's W/H use the
horizontal and vertical units, as the Control and Properties fields do.

Test: tool_readouts_measure_in_the_documents_units (picas before).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CgGsJkVe5GYG9qK6VFdECa

crates/tools/src/nav.rs

@@ -434,8 +434,8 @@ impl Tool for PageTool {
                 p: d.cur,
                 text: format!(
                     "W: {}\nH: {}",
-                    designcraft_geom::format_measure(pg.width, cx.unit),
-                    designcraft_geom::format_measure(pg.height, cx.unit)
+                    designcraft_geom::format_measure(pg.width, cx.doc.settings.horizontal_units),
+                    designcraft_geom::format_measure(pg.height, cx.doc.settings.vertical_units)
                 ),
             });
         }

crates/ui-egui/src/lib.rs

@@ -737,7 +737,9 @@ impl DesignApp {
         ViewInfo {
             zoom: self.view().map(|v| v.zoom).unwrap_or(1.0),
             snap: self.ui.snap_view(),
-            unit: self.ui.units,
+            // Tool readouts (sizes, smart-guide distances) measure in the document's ruler units,
+            // as its Control and Properties fields do.
+            unit: self.session.active().map_or(self.ui.units, |st| st.doc.settings.horizontal_units),
             stroke_in_front: self.ui.stroke_front,
         }
     }
@@ -1843,6 +1845,17 @@ mod tests {
         assert!(!accurate.rich_black, "a saved choice is kept");
     }
 
+    /// Tool readouts measured in picas whatever the document's units (the UI's unit is never set):
+    /// they follow the active document's ruler units.
+    #[test]
+    fn tool_readouts_measure_in_the_documents_units() {
+        let mut app = DesignApp::new(designcraft_engine::Session::new(), Services::default());
+        assert_eq!(app.view_info().unit, Unit::Picas, "no document: the UI's default");
+        app.run("file.new", json!({})).unwrap();
+        app.run("document.preferences", json!({"horizontalUnits": "inches", "verticalUnits": "millimeters"})).unwrap();
+        assert_eq!(app.view_info().unit, Unit::Inches);
+    }
+
     /// An app with one document that has an unsaved edit.
     fn app_with_unsaved_document() -> DesignApp {
         let mut app = DesignApp::new(designcraft_engine::Session::new(), Services::default());