agent: Return ToolResult from run inside Tool (#28763)

This is just a refactor which adds no functionality.
We now return a `ToolResult` from `Tool > run(...)`. For now this just
wraps the output task in a struct. We'll use this to implement custom
rendering of tools, see #28621.

Release Notes:

- N/A

crates/assistant_tools/src/batch_tool.rs

@@ -1,6 +1,6 @@
 use crate::schema::json_schema_for;
 use anyhow::{Result, anyhow};
-use assistant_tool::{ActionLog, Tool, ToolWorkingSet};
+use assistant_tool::{ActionLog, Tool, ToolResult, ToolWorkingSet};
 use futures::future::join_all;
 use gpui::{App, AppContext, Entity, Task};
 use language_model::{LanguageModelRequestMessage, LanguageModelToolSchemaFormat};
@@ -219,14 +219,14 @@ impl Tool for BatchTool {
         project: Entity<Project>,
         action_log: Entity<ActionLog>,
         cx: &mut App,
-    ) -> Task<Result<String>> {
+    ) -> ToolResult {
         let input = match serde_json::from_value::<BatchToolInput>(input) {
             Ok(input) => input,
-            Err(err) => return Task::ready(Err(anyhow!(err))),
+            Err(err) => return Task::ready(Err(anyhow!(err))).into(),
         };
 
         if input.invocations.is_empty() {
-            return Task::ready(Err(anyhow!("No tool invocations provided")));
+            return Task::ready(Err(anyhow!("No tool invocations provided"))).into();
         }
 
         let run_tools_concurrently = input.run_tools_concurrently;
@@ -257,11 +257,11 @@ impl Tool for BatchTool {
                     let project = project.clone();
                     let action_log = action_log.clone();
                     let messages = messages.clone();
-                    let task = cx
+                    let tool_result = cx
                         .update(|cx| tool.run(invocation.input, &messages, project, action_log, cx))
                         .map_err(|err| anyhow!("Failed to start tool '{}': {}", tool_name, err))?;
 
-                    tasks.push(task);
+                    tasks.push(tool_result.output);
                 }
 
                 Ok((tasks, tool_names))
@@ -306,5 +306,6 @@ impl Tool for BatchTool {
 
             Ok(formatted_results.trim().to_string())
         })
+        .into()
     }
 }