agent: Refine the web search tool call UI (#29190)

This PR refines a bit the web search tool UI by introducing a component
(`ToolCallCardHeader`) that aims to standardize the heading element of
tool calls in the thread.

In terms of next steps, I plan to evolve this component further soon
(e.g., building a full-blown "tool call card" component), and even move
it to a place where I can re-use it in the active_thread as well without
making the `assistant_tools` a dependency of it.

Release Notes:

- N/A

crates/assistant_tools/src/ui/tool_call_card_header.rs

@@ -0,0 +1,102 @@
+use gpui::{Animation, AnimationExt, App, IntoElement, pulsating_between};
+use std::time::Duration;
+use ui::{Tooltip, prelude::*};
+
+/// A reusable header component for tool call cards.
+#[derive(IntoElement)]
+pub struct ToolCallCardHeader {
+    icon: IconName,
+    primary_text: SharedString,
+    secondary_text: Option<SharedString>,
+    is_loading: bool,
+    error: Option<String>,
+}
+
+impl ToolCallCardHeader {
+    pub fn new(icon: IconName, primary_text: impl Into<SharedString>) -> Self {
+        Self {
+            icon,
+            primary_text: primary_text.into(),
+            secondary_text: None,
+            is_loading: false,
+            error: None,
+        }
+    }
+
+    pub fn with_secondary_text(mut self, text: impl Into<SharedString>) -> Self {
+        self.secondary_text = Some(text.into());
+        self
+    }
+
+    pub fn loading(mut self) -> Self {
+        self.is_loading = true;
+        self
+    }
+
+    pub fn with_error(mut self, error: impl Into<String>) -> Self {
+        self.error = Some(error.into());
+        self
+    }
+}
+
+impl RenderOnce for ToolCallCardHeader {
+    fn render(self, window: &mut Window, cx: &mut App) -> impl IntoElement {
+        let font_size = rems(0.8125);
+        let secondary_text = self.secondary_text;
+
+        h_flex()
+            .id("tool-label-container")
+            .gap_1p5()
+            .max_w_full()
+            .overflow_x_scroll()
+            .opacity(0.8)
+            .child(
+                h_flex().h(window.line_height()).justify_center().child(
+                    Icon::new(self.icon)
+                        .size(IconSize::XSmall)
+                        .color(Color::Muted),
+                ),
+            )
+            .child(
+                h_flex()
+                    .h(window.line_height())
+                    .gap_1p5()
+                    .text_size(font_size)
+                    .map(|this| {
+                        if let Some(error) = &self.error {
+                            this.child(format!("{} failed", self.primary_text)).child(
+                                IconButton::new("error_info", IconName::Warning)
+                                    .shape(ui::IconButtonShape::Square)
+                                    .icon_size(IconSize::XSmall)
+                                    .icon_color(Color::Warning)
+                                    .tooltip(Tooltip::text(error.clone())),
+                            )
+                        } else {
+                            this.child(self.primary_text.clone())
+                        }
+                    })
+                    .when_some(secondary_text, |this, secondary_text| {
+                        this.child(
+                            div()
+                                .size(px(3.))
+                                .rounded_full()
+                                .bg(cx.theme().colors().text),
+                        )
+                        .child(div().text_size(font_size).child(secondary_text.clone()))
+                    })
+                    .with_animation(
+                        "loading-label",
+                        Animation::new(Duration::from_secs(2))
+                            .repeat()
+                            .with_easing(pulsating_between(0.6, 1.)),
+                        move |this, delta| {
+                            if self.is_loading {
+                                this.opacity(delta)
+                            } else {
+                                this
+                            }
+                        },
+                    ),
+            )
+    }
+}