fix(properties): close the color dropdown on selection change and viewport click

The Properties color dropdown stayed open after deselecting, reselecting, or
clicking into the viewport. refresh_properties carried color_picker_open across
rebuilds, so a selection change never closed it; and a viewport press starts a
box selection, so it only closed on the second click. Stop preserving the
picker state across rebuilds and dismiss both color dropdowns on the first
viewport press.

Fixes #104.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/update.rs

@@ -2779,6 +2779,11 @@ impl OpenCADStudio {
                 // (e.g. the annotation style combo), which has no backdrop of
                 // its own to catch outside clicks.
                 self.ribbon.close_dropdown();
+                // Likewise dismiss the Properties color dropdowns — a viewport
+                // press starts a box selection, so without this they'd only
+                // close on the second click (issue #104).
+                self.tabs[i].properties.color_picker_open = false;
+                self.tabs[i].properties.color_palette_open = false;
                 // Click anywhere outside the popup dismisses it. The
                 // menu's own buttons live above this mouse_area, so a
                 // press that reaches here means the cursor is not on