Canvas · Tools: single handles, a wrapping palette, the pen ends with its tool

Handles resize one shape, so a selection of several shows its outline
and no handles; a press there no longer falls through to a marquee.
ToggleGroup wraps its faces when narrow, so the ToolPalette stays in a
280px box. A pen path left open ends when the tool changes: two points
or more go to the owner after the frame, a lone point is dropped, and
the open path paints only while the pen is the tool.

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

src/canvas/marks.rs

@@ -1,4 +1,7 @@
-use gpui::{App, Hsla, IntoElement, ParentElement, Pixels, RenderOnce, Styled, Window, div};
+use gpui::{
+    App, Hsla, InteractiveElement, IntoElement, ParentElement, Pixels, RenderOnce, Styled, Window,
+    div,
+};
 
 use super::{
     edit::Handle,
@@ -8,7 +11,7 @@ use super::{
 use crate::theme::ActiveTheme;
 
 /// A box in view pixels as an absolute element.
-fn placed(frame: &Frame) -> gpui::Div {
+pub(super) fn placed(frame: &Frame) -> gpui::Div {
     div()
         .absolute()
         .left(Pixels::from(frame.x))
@@ -73,7 +76,13 @@ impl RenderOnce for TransformHandles {
         let side = f32::from(theme.canvas().handle.to_pixels(window.rem_size()));
         let squares = handle_boxes(&self.frame, side)
             .into_iter()
-            .map(move |(_, frame)| placed(&frame).bg(surface).border_1().border_color(accent));
+            .map(move |(handle, frame)| {
+                placed(&frame)
+                    .bg(surface)
+                    .border_1()
+                    .border_color(accent)
+                    .debug_selector(move || format!("handle {handle:?}"))
+            });
         div()
             .absolute()
             .inset_0()