assistant2: Navigate context strip with keyboard (#23128)

Context pills are now focusable and intractable via the keyboard.

- <kbd>←</kbd> and <kbd>→</kbd> move the focus to the previous or next
item (wrapping if necessary)
- <kbd>↓</kbd> and <kbd>↑</kbd> move the focus vertically
- If the cursor is in the first/last row of the assistant/inline editor,
they will move the focus to the strip
- Inside the strip, they will move the focus to the pill horizontally
overlapping the most
- If already in the first/last row of the strip, they will move to the
first/last pill (like in editors)
- If the first/last pill is focused, they will move the focus back to
the editor
- <kbd>⌫</kbd>  removes the focused pill (unless it's the suggested one)
- <kbd>⏎</kbd> accepts the suggested pill if focused
  


https://github.com/user-attachments/assets/040bc71c-a3ae-4961-9886-2d5c3d290a73



Release Notes:

- N/A

crates/assistant2/src/ui/context_pill.rs

@@ -10,13 +10,16 @@ pub enum ContextPill {
     Added {
         context: ContextSnapshot,
         dupe_name: bool,
+        focused: bool,
+        on_click: Option<Rc<dyn Fn(&ClickEvent, &mut WindowContext)>>,
         on_remove: Option<Rc<dyn Fn(&ClickEvent, &mut WindowContext)>>,
     },
     Suggested {
         name: SharedString,
         icon_path: Option<SharedString>,
         kind: ContextKind,
-        on_add: Rc<dyn Fn(&ClickEvent, &mut WindowContext)>,
+        focused: bool,
+        on_click: Option<Rc<dyn Fn(&ClickEvent, &mut WindowContext)>>,
     },
 }
 
@@ -24,12 +27,15 @@ impl ContextPill {
     pub fn new_added(
         context: ContextSnapshot,
         dupe_name: bool,
+        focused: bool,
         on_remove: Option<Rc<dyn Fn(&ClickEvent, &mut WindowContext)>>,
     ) -> Self {
         Self::Added {
             context,
             dupe_name,
             on_remove,
+            focused,
+            on_click: None,
         }
     }
 
@@ -37,16 +43,29 @@ impl ContextPill {
         name: SharedString,
         icon_path: Option<SharedString>,
         kind: ContextKind,
-        on_add: Rc<dyn Fn(&ClickEvent, &mut WindowContext)>,
+        focused: bool,
     ) -> Self {
         Self::Suggested {
             name,
             icon_path,
             kind,
-            on_add,
+            focused,
+            on_click: None,
         }
     }
 
+    pub fn on_click(mut self, listener: Rc<dyn Fn(&ClickEvent, &mut WindowContext)>) -> Self {
+        match &mut self {
+            ContextPill::Added { on_click, .. } => {
+                *on_click = Some(listener);
+            }
+            ContextPill::Suggested { on_click, .. } => {
+                *on_click = Some(listener);
+            }
+        }
+        self
+    }
+
     pub fn id(&self) -> ElementId {
         match self {
             Self::Added { context, .. } => {
@@ -93,9 +112,15 @@ impl RenderOnce for ContextPill {
                 context,
                 dupe_name,
                 on_remove,
+                focused,
+                on_click,
             } => base_pill
                 .bg(color.element_background)
-                .border_color(color.border.opacity(0.5))
+                .border_color(if *focused {
+                    color.border_focused
+                } else {
+                    color.border.opacity(0.5)
+                })
                 .pr(if on_remove.is_some() { px(2.) } else { px(4.) })
                 .child(
                     h_flex()
@@ -128,16 +153,25 @@ impl RenderOnce for ContextPill {
                                 move |event, cx| on_remove(event, cx)
                             }),
                     )
+                })
+                .when_some(on_click.as_ref(), |element, on_click| {
+                    let on_click = on_click.clone();
+                    element.on_click(move |event, cx| on_click(event, cx))
                 }),
             ContextPill::Suggested {
                 name,
                 icon_path: _,
                 kind,
-                on_add,
+                focused,
+                on_click,
             } => base_pill
                 .cursor_pointer()
                 .pr_1()
-                .border_color(color.border_variant.opacity(0.5))
+                .border_color(if *focused {
+                    color.border_focused
+                } else {
+                    color.border_variant.opacity(0.5)
+                })
                 .hover(|style| style.bg(color.element_hover.opacity(0.5)))
                 .child(
                     Label::new(name.clone())
@@ -162,9 +196,9 @@ impl RenderOnce for ContextPill {
                         .into_any_element(),
                 )
                 .tooltip(|cx| Tooltip::with_meta("Suggested Context", None, "Click to add it", cx))
-                .on_click({
-                    let on_add = on_add.clone();
-                    move |event, cx| on_add(event, cx)
+                .when_some(on_click.as_ref(), |element, on_click| {
+                    let on_click = on_click.clone();
+                    element.on_click(move |event, cx| on_click(event, cx))
                 }),
         }
     }