Show prompt usage in agent overflow menu (#29922)

This PR adds prompt usage information, and easy access to managing your
account, to the agent overflow menu:

![CleanShot 2025-05-05 at 10 04
20@2x](https://github.com/user-attachments/assets/337a1a0b-6f71-49a0-9fe7-4fbf2ec1fc27)

Currently this UI will only show after making a request. We'll work on
eagerly getting the usage info later.

Release Notes:

- Added current prompt usage information to the agent menu (`...`) for
Zed AI users

crates/ui/src/components/context_menu.rs

@@ -16,6 +16,8 @@ use super::Tooltip;
 pub enum ContextMenuItem {
     Separator,
     Header(SharedString),
+    /// title, link_label, link_url
+    HeaderWithLink(SharedString, SharedString, SharedString), // This could be folded into header
     Label(SharedString),
     Entry(ContextMenuEntry),
     CustomEntry {
@@ -332,6 +334,20 @@ impl ContextMenu {
         self
     }
 
+    pub fn header_with_link(
+        mut self,
+        title: impl Into<SharedString>,
+        link_label: impl Into<SharedString>,
+        link_url: impl Into<SharedString>,
+    ) -> Self {
+        self.items.push(ContextMenuItem::HeaderWithLink(
+            title.into(),
+            link_label.into(),
+            link_url.into(),
+        ));
+        self
+    }
+
     pub fn separator(mut self) -> Self {
         self.items.push(ContextMenuItem::Separator);
         self
@@ -788,6 +804,25 @@ impl ContextMenu {
             ContextMenuItem::Header(header) => ListSubHeader::new(header.clone())
                 .inset(true)
                 .into_any_element(),
+            ContextMenuItem::HeaderWithLink(header, label, url) => {
+                let url = url.clone();
+                let link_id = ElementId::Name(format!("link-{}", url).into());
+                ListSubHeader::new(header.clone())
+                    .inset(true)
+                    .end_slot(
+                        Button::new(link_id, label.clone())
+                            .color(Color::Muted)
+                            .label_size(LabelSize::Small)
+                            .size(ButtonSize::None)
+                            .style(ButtonStyle::Transparent)
+                            .on_click(move |_, _, cx| {
+                                let url = url.clone();
+                                cx.open_url(&url);
+                            })
+                            .into_any_element(),
+                    )
+                    .into_any_element()
+            }
             ContextMenuItem::Label(label) => ListItem::new(ix)
                 .inset(true)
                 .disabled(true)
@@ -1057,6 +1092,7 @@ impl ContextMenuItem {
     fn is_selectable(&self) -> bool {
         match self {
             ContextMenuItem::Header(_)
+            | ContextMenuItem::HeaderWithLink(_, _, _)
             | ContextMenuItem::Separator
             | ContextMenuItem::Label { .. } => false,
             ContextMenuItem::Entry(ContextMenuEntry { disabled, .. }) => !disabled,

crates/ui/src/components/list/list_sub_header.rs

@@ -5,6 +5,7 @@ use crate::{Icon, IconName, IconSize, Label, h_flex};
 pub struct ListSubHeader {
     label: SharedString,
     start_slot: Option<IconName>,
+    end_slot: Option<AnyElement>,
     inset: bool,
     selected: bool,
 }
@@ -14,6 +15,7 @@ impl ListSubHeader {
         Self {
             label: label.into(),
             start_slot: None,
+            end_slot: None,
             inset: false,
             selected: false,
         }
@@ -24,6 +26,11 @@ impl ListSubHeader {
         self
     }
 
+    pub fn end_slot(mut self, end_slot: AnyElement) -> Self {
+        self.end_slot = Some(end_slot);
+        self
+    }
+
     pub fn inset(mut self, inset: bool) -> Self {
         self.inset = inset;
         self
@@ -73,7 +80,8 @@ impl RenderOnce for ListSubHeader {
                                     .color(Color::Muted)
                                     .size(LabelSize::Small),
                             ),
-                    ),
+                    )
+                    .children(self.end_slot),
             )
     }
 }