Fix forward Delete key icon (#65037)

<img width="2940" height="1720" alt="keymap-dark"
src="https://github.com/user-attachments/assets/f4c28b4f-6a33-4479-a24f-c95d64a790c3"
/>
Closes #64964.

Use a dedicated forward Delete icon (⌦) instead of Backspace (⌫). Add a
regression test for distinct icons.

Release Notes:

- Fixed identical Backspace and Delete icons in the keymap editor.

assets/icons/delete.svg

@@ -0,0 +1,7 @@
+<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
+<g transform="translate(16 0) scale(-1 1)">
+<path d="M6.79998 4C6.50183 4.00002 6.21436 4.10574 5.99358 4.29657L2.19677 7.57657C2.1348 7.63013 2.08528 7.69545 2.05139 7.76832C2.01751 7.8412 2 7.92001 2 7.99971C2 8.07941 2.01751 8.15823 2.05139 8.23111C2.08528 8.30398 2.1348 8.36929 2.19677 8.42286L5.99358 11.7034C6.21436 11.8943 6.50183 12 6.79998 12H12.8C13.1183 12 13.4235 11.8796 13.6485 11.6653C13.8736 11.4509 14 11.1602 14 10.8571V5.14286C14 4.83975 13.8736 4.54906 13.6485 4.33474C13.4235 4.12041 13.1183 4 12.8 4H6.79998Z" stroke="black" stroke-width="1.2" stroke-linecap="round" stroke-linejoin="round"/>
+<path d="M8.5 6.5L11.5 9.5" stroke="black" stroke-width="1.2" stroke-linecap="round" stroke-linejoin="round"/>
+<path d="M11.5 6.5L8.5 9.5" stroke="black" stroke-width="1.2" stroke-linecap="round" stroke-linejoin="round"/>
+</g>
+</svg>

crates/icons/src/icons.rs

@@ -101,6 +101,7 @@ pub enum IconName {
     DebugStepInto,
     DebugStepOut,
     DebugStepOver,
+    Delete,
     Diff,
     DiffSplit,
     DiffSplitAuto,

crates/ui/src/components/keybinding.rs

@@ -392,7 +392,7 @@ fn icon_for_key(key: &str, platform_style: PlatformStyle) -> Option<IconName> {
         "up" => Some(IconName::ArrowUp),
         "down" => Some(IconName::ArrowDown),
         "backspace" => Some(IconName::Backspace),
-        "delete" => Some(IconName::Backspace),
+        "delete" => Some(IconName::Delete),
         "return" => Some(IconName::Return),
         "enter" => Some(IconName::Return),
         "tab" => Some(IconName::Tab),
@@ -848,6 +848,21 @@ impl Component for KeyBinding {
 mod tests {
     use super::*;
 
+    #[test]
+    fn test_backspace_and_delete_have_distinct_icons() {
+        for platform_style in [
+            PlatformStyle::Mac,
+            PlatformStyle::Linux,
+            PlatformStyle::Windows,
+        ] {
+            let backspace = icon_for_key("backspace", platform_style);
+            let delete = icon_for_key("delete", platform_style);
+            assert!(backspace.is_some());
+            assert!(delete.is_some());
+            assert_ne!(backspace, delete);
+        }
+    }
+
     #[test]
     fn test_text_for_keystroke() {
         let keystroke = Keystroke::parse("cmd-c").unwrap();