assistant2: Add ability to fetch URLs as context (#21988)

This PR adds the ability to fetch URLs as context in Assistant2.

In the picker we use the search area as an input for the user to enter
the URL they wish to fetch:

<img width="1159" alt="Screenshot 2024-12-13 at 2 45 41 PM"
src="https://github.com/user-attachments/assets/b3b20648-2c22-4509-b592-d0291d25b202"
/>

<img width="1159" alt="Screenshot 2024-12-13 at 2 45 47 PM"
src="https://github.com/user-attachments/assets/7e6bab2d-2731-467f-9781-130c6e4ea5cf"
/>

Release Notes:

- N/A

crates/assistant2/src/context_picker.rs

@@ -1,3 +1,4 @@
+mod fetch_context_picker;
 mod file_context_picker;
 
 use std::sync::Arc;
@@ -11,6 +12,7 @@ use ui::{prelude::*, ListItem, ListItemSpacing, Tooltip};
 use util::ResultExt;
 use workspace::Workspace;
 
+use crate::context_picker::fetch_context_picker::FetchContextPicker;
 use crate::context_picker::file_context_picker::FileContextPicker;
 use crate::message_editor::MessageEditor;
 
@@ -18,6 +20,7 @@ use crate::message_editor::MessageEditor;
 enum ContextPickerMode {
     Default,
     File(View<FileContextPicker>),
+    Fetch(View<FetchContextPicker>),
 }
 
 pub(super) struct ContextPicker {
@@ -47,7 +50,7 @@ impl ContextPicker {
                     icon: IconName::File,
                 },
                 ContextPickerEntry {
-                    name: "web".into(),
+                    name: "fetch".into(),
                     description: "Fetch content from URL".into(),
                     icon: IconName::Globe,
                 },
@@ -77,16 +80,21 @@ impl FocusableView for ContextPicker {
         match &self.mode {
             ContextPickerMode::Default => self.picker.focus_handle(cx),
             ContextPickerMode::File(file_picker) => file_picker.focus_handle(cx),
+            ContextPickerMode::Fetch(fetch_picker) => fetch_picker.focus_handle(cx),
         }
     }
 }
 
 impl Render for ContextPicker {
     fn render(&mut self, _cx: &mut ViewContext<Self>) -> impl IntoElement {
-        v_flex().min_w(px(400.)).map(|parent| match &self.mode {
-            ContextPickerMode::Default => parent.child(self.picker.clone()),
-            ContextPickerMode::File(file_picker) => parent.child(file_picker.clone()),
-        })
+        v_flex()
+            .w(px(400.))
+            .min_w(px(400.))
+            .map(|parent| match &self.mode {
+                ContextPickerMode::Default => parent.child(self.picker.clone()),
+                ContextPickerMode::File(file_picker) => parent.child(file_picker.clone()),
+                ContextPickerMode::Fetch(fetch_picker) => parent.child(fetch_picker.clone()),
+            })
     }
 }
 
@@ -144,6 +152,16 @@ impl PickerDelegate for ContextPickerDelegate {
                                 )
                             }));
                         }
+                        "fetch" => {
+                            this.mode = ContextPickerMode::Fetch(cx.new_view(|cx| {
+                                FetchContextPicker::new(
+                                    self.context_picker.clone(),
+                                    self.workspace.clone(),
+                                    self.message_editor.clone(),
+                                    cx,
+                                )
+                            }));
+                        }
                         _ => {}
                     }
 
@@ -157,7 +175,7 @@ impl PickerDelegate for ContextPickerDelegate {
         self.context_picker
             .update(cx, |this, cx| match this.mode {
                 ContextPickerMode::Default => cx.emit(DismissEvent),
-                ContextPickerMode::File(_) => {}
+                ContextPickerMode::File(_) | ContextPickerMode::Fetch(_) => {}
             })
             .log_err();
     }