Delete for everything: selection.delete removes sketch entities, features and sketches (with their dependents), construction planes, bodies (Remove feature), occurrences and components, and canvases in one undo step, with a dry run; Delete/Backspace and every menu's Delete go through it and ask first, listing what goes with it and what would fail; faces say Delete Face is not available yet; ui.confirm control method

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AS5Tn3xieewUSg3uxrMVdL

crates/ui-egui/src/browser.rs

@@ -32,6 +32,8 @@ pub struct TreeState {
     pub redefine: Option<u64>,
     /// Components picked in the tree (they have no viewport selection).
     pub picked_components: Vec<u64>,
+    /// Canvases picked in the tree.
+    pub picked_canvases: Vec<u64>,
     /// The last row clicked (for Shift ranges).
     anchor: Option<String>,
     /// Row keys in drawing order this frame (for Shift ranges).