Render messages as early as possible to show progress (#11569)

This shows "Researching..." as placeholder text as early as possible so
that the user can see the model is working on reading/researching/etc.

This also adds on an `Option<Value>` to the `render_running` function so
that tools can hopefully render based on partially completed JSON (still
to come).

Release Notes:

- N/A

crates/assistant2/src/assistant2.rs

@@ -16,7 +16,8 @@ use crate::{
 use ::ui::{div, prelude::*, Color, Tooltip, ViewContext};
 use anyhow::{Context, Result};
 use assistant_tooling::{
-    AttachmentRegistry, ProjectContext, ToolFunctionCall, ToolRegistry, UserAttachment,
+    tool_running_placeholder, AttachmentRegistry, ProjectContext, ToolFunctionCall, ToolRegistry,
+    UserAttachment,
 };
 use client::{proto, Client, UserStore};
 use collections::HashMap;
@@ -864,6 +865,10 @@ impl AssistantChat {
                     }
                 }
 
+                if message_elements.is_empty() {
+                    message_elements.push(tool_running_placeholder());
+                }
+
                 div()
                     .when(is_first, |this| this.pt(padding))
                     .child(

crates/assistant2/src/tools/project_index.rs

@@ -6,6 +6,7 @@ use project::ProjectPath;
 use schemars::JsonSchema;
 use semantic_index::{ProjectIndex, Status};
 use serde::Deserialize;
+use serde_json::Value;
 use std::{fmt::Write as _, ops::Range};
 use ui::{div, prelude::*, CollapsibleContainer, Color, Icon, IconName, Label, WindowContext};
 
@@ -202,8 +203,14 @@ impl LanguageModelTool for ProjectIndexTool {
         cx.new_view(|_cx| ProjectIndexView::new(input, output))
     }
 
-    fn render_running(_: &mut WindowContext) -> impl IntoElement {
-        CollapsibleContainer::new(ElementId::Name(nanoid::nanoid!().into()), false)
-            .start_slot("Searching code base")
+    fn render_running(arguments: &Option<Value>, _: &mut WindowContext) -> impl IntoElement {
+        let text: String = arguments
+            .as_ref()
+            .and_then(|arguments| arguments.get("query"))
+            .and_then(|query| query.as_str())
+            .map(|query| format!("Searching for: {}", query))
+            .unwrap_or_else(|| "Preparing search...".to_string());
+
+        CollapsibleContainer::new(ElementId::Name(nanoid::nanoid!().into()), false).start_slot(text)
     }
 }