feat(dock): migrate block palette onto general edge-stack dock

Pin/close/resize/drag-between-edges/auto-collapse hover, themed and
persisted, mirroring the properties panel chrome.

src/app/update/mod.rs

@@ -6336,6 +6336,7 @@ impl OpenCADStudio {
             Message::PlotDialogOpen => self.on_plot_dialog_open(),
             Message::PlotDlg(m) => self.on_plot_dlg(m),
             Message::BlockPalette(m) => self.on_block_palette(m),
+            Message::Dock(m) => self.on_dock(m),
             Message::PrintAllOpen => self.on_print_all_open(),
             Message::PrintAllToggle(name) => {
                 if let Some((_, selected)) = self