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/control/entities.rs

@@ -676,7 +676,7 @@ impl OpenCADStudio {
 /// Silent no-op for an unknown name (callers validate first);
 /// `*`-prefixed layout records are rejected by the callers. Returns the
 /// number of entities erased.
-fn erase_block_definition(scene: &mut crate::scene::Scene, name: &str) -> usize {
+pub(crate) fn erase_block_definition(scene: &mut crate::scene::Scene, name: &str) -> usize {
     let Some(record) = scene.document.block_records.get(name) else {
         return 0;
     };