Blocks palette: tabs, options, drag insertion and -INSERT

Rebuild the Blocks palette with Current Drawing / Recent / Favorites /
Libraries tabs, wildcard filter, six views, insertion options, click and
drop insertion and a block context menu. INSERT opens the palette, the
new -INSERT runs on the command line, the ribbon Insert button becomes a
block gallery, and BLOCKMRULIST, BLOCKREDEFINEMODE, BLOCKNAVIGATE,
BLOCKSTATE, EXPLMODE and INSNAME are added.

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

src/app/update/viewport.rs

@@ -3356,6 +3356,7 @@ impl OpenCADStudio {
 
     pub(super) fn on_viewport_left_press(&mut self) -> Task<Message> {
         let i = self.active_tab;
+        self.block_palette.pressed = None;
         if let Some(command) = self.tabs[i].active_cmd.as_mut() {
             command.set_ctrl(self.ctrl_down);
             command.set_shift(self.shift_down);
@@ -3724,6 +3725,10 @@ impl OpenCADStudio {
 
     pub(super) fn on_viewport_left_release(&mut self) -> Task<Message> {
         let i = self.active_tab;
+        // A block dragged from the Blocks palette lands here.
+        if let Some(item) = self.take_block_drop() {
+            return self.drop_block(item);
+        }
         if let Some(command) = self.tabs[i].active_cmd.as_mut() {
             command.set_ctrl(self.ctrl_down);
             command.set_shift(self.shift_down);