fix(xref): tessellate xref'd solids so they render (#203)

XREFs are merged into the document on the UI thread AFTER the background
worker already built the mesh caches, so those caches contained none of
the xref'd geometry. The wire pass rebuilds from the document each frame
(bump_geometry covers it), but 3D-solid meshes are only produced by
populate_meshes_from_document, which never re-ran after the merge — so
xref'd solids (walls, floors, roofs) were loaded but never tessellated
and never drawn. Re-run it once a xref actually resolves.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/app/update/file.rs

@@ -286,6 +286,7 @@ pub(super) fn on_open_file(&mut self) -> Task<Message> {
 
                 // Auto-resolve XREFs relative to the opened file's directory.
                 let mut xref_ms = 0u32;
+                let mut xref_merged = false;
                 if let Some(base_dir) = path.parent() {
                     // xref content arrives un-purged: parser-garbage entities
                     // inside the referenced file can trigger infinite loops in
@@ -304,6 +305,7 @@ pub(super) fn on_open_file(&mut self) -> Task<Message> {
                     for info in &xrefs {
                         match info.status {
                             crate::io::xref::XrefStatus::Loaded => {
+                                xref_merged = true;
                                 self.command_line
                                     .push_output(&format!("XREF  Loaded \"{}\"", info.name));
                             }
@@ -344,6 +346,15 @@ pub(super) fn on_open_file(&mut self) -> Task<Message> {
                 self.tabs[i].scene.block_meshes = caches.block_meshes;
                 // Invalidate the wire cache so the new document is tessellated.
                 self.tabs[i].scene.bump_geometry();
+                // XREFs are merged into the document AFTER the background worker
+                // built the mesh caches above, so those caches contain none of
+                // the xref'd geometry. The wire pass rebuilds from the document
+                // each frame (bump_geometry covers it), but 3D-solid meshes are
+                // only tessellated by `populate_meshes_from_document` — re-run it
+                // so xref'd solids (walls, floors, roofs) actually render. (#203)
+                if xref_merged {
+                    self.tabs[i].scene.populate_meshes_from_document();
+                }
                 self.tabs[i].scene.selected = rustc_hash::FxHashSet::default();
                 self.tabs[i].scene.preview_wires = vec![];
                 self.tabs[i].scene.current_layout = "Model".to_string();