assistant tools: Add Tool::icon method instead of matching on name (#27444)

Release Notes:

- N/A

crates/assistant_tools/src/create_file_tool.rs

@@ -6,6 +6,7 @@ use project::Project;
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
 use std::sync::Arc;
+use ui::IconName;
 
 #[derive(Debug, Serialize, Deserialize, JsonSchema)]
 pub struct CreateFileToolInput {
@@ -44,6 +45,10 @@ impl Tool for CreateFileTool {
         include_str!("./create_file_tool/description.md").into()
     }
 
+    fn icon(&self) -> IconName {
+        IconName::File
+    }
+
     fn input_schema(&self) -> serde_json::Value {
         let schema = schemars::schema_for!(CreateFileToolInput);
         serde_json::to_value(&schema).unwrap()