agent: Display full terminal output without scrolling (#31922)

The terminal tool card used a fixed height and scrolling, but this meant
that it was too tall for commands that only outputted a few lines, and
the nested scrolling was undesirable.

This PR makes the card be as too as needed to fit the entire output (no
scrolling), and allows the user to collapse it to fewer lines when
applicable. Making it work the same way as the edit tool card. In fact,
both tools now use a shared UI component.


https://github.com/user-attachments/assets/1127e21d-1d41-4a4b-a99f-7cd70fccbb56


Release Notes:

- Agent: Display full terminal output
- Agent: Allow collapsing terminal output

crates/assistant_tools/src/ui/tool_output_preview.rs

@@ -0,0 +1,115 @@
+use gpui::{AnyElement, EntityId, prelude::*};
+use ui::{Tooltip, prelude::*};
+
+#[derive(IntoElement)]
+pub struct ToolOutputPreview<F>
+where
+    F: Fn(bool, &mut Window, &mut App) + 'static,
+{
+    content: AnyElement,
+    entity_id: EntityId,
+    full_height: bool,
+    total_lines: usize,
+    collapsed_fade: bool,
+    on_toggle: Option<F>,
+}
+
+pub const COLLAPSED_LINES: usize = 10;
+
+impl<F> ToolOutputPreview<F>
+where
+    F: Fn(bool, &mut Window, &mut App) + 'static,
+{
+    pub fn new(content: AnyElement, entity_id: EntityId) -> Self {
+        Self {
+            content,
+            entity_id,
+            full_height: true,
+            total_lines: 0,
+            collapsed_fade: false,
+            on_toggle: None,
+        }
+    }
+
+    pub fn with_total_lines(mut self, total_lines: usize) -> Self {
+        self.total_lines = total_lines;
+        self
+    }
+
+    pub fn toggle_state(mut self, full_height: bool) -> Self {
+        self.full_height = full_height;
+        self
+    }
+
+    pub fn with_collapsed_fade(mut self) -> Self {
+        self.collapsed_fade = true;
+        self
+    }
+
+    pub fn on_toggle(mut self, listener: F) -> Self {
+        self.on_toggle = Some(listener);
+        self
+    }
+}
+
+impl<F> RenderOnce for ToolOutputPreview<F>
+where
+    F: Fn(bool, &mut Window, &mut App) + 'static,
+{
+    fn render(self, _window: &mut Window, cx: &mut App) -> impl IntoElement {
+        if self.total_lines <= COLLAPSED_LINES {
+            return self.content;
+        }
+        let border_color = cx.theme().colors().border.opacity(0.6);
+
+        let (icon, tooltip_label) = if self.full_height {
+            (IconName::ChevronUp, "Collapse")
+        } else {
+            (IconName::ChevronDown, "Expand")
+        };
+
+        let gradient_overlay =
+            if self.collapsed_fade && !self.full_height {
+                Some(div().absolute().bottom_5().left_0().w_full().h_2_5().bg(
+                    gpui::linear_gradient(
+                        0.,
+                        gpui::linear_color_stop(cx.theme().colors().editor_background, 0.),
+                        gpui::linear_color_stop(
+                            cx.theme().colors().editor_background.opacity(0.),
+                            1.,
+                        ),
+                    ),
+                ))
+            } else {
+                None
+            };
+
+        v_flex()
+            .relative()
+            .child(self.content)
+            .children(gradient_overlay)
+            .child(
+                h_flex()
+                    .id(("expand-button", self.entity_id))
+                    .flex_none()
+                    .cursor_pointer()
+                    .h_5()
+                    .justify_center()
+                    .border_t_1()
+                    .rounded_b_md()
+                    .border_color(border_color)
+                    .bg(cx.theme().colors().editor_background)
+                    .hover(|style| style.bg(cx.theme().colors().element_hover.opacity(0.1)))
+                    .child(Icon::new(icon).size(IconSize::Small).color(Color::Muted))
+                    .tooltip(Tooltip::text(tooltip_label))
+                    .when_some(self.on_toggle, |this, on_toggle| {
+                        this.on_click({
+                            move |_, window, cx| {
+                                on_toggle(!self.full_height, window, cx);
+                            }
+                        })
+                    }),
+            )
+            .into_any()
+    }
+}