assistant_tool: Decouple Tool from Workspace (#26309)

This PR decouples the `Tool` trait from the `Workspace` (and from the
UI, in general).

`Tool::run` now takes a `WeakEntity<Project>` instead of a
`WeakEntity<Workspace>` and a `Window`.

Release Notes:

- N/A

crates/assistant_tools/src/read_file_tool.rs

@@ -3,11 +3,10 @@ use std::sync::Arc;
 
 use anyhow::{anyhow, Result};
 use assistant_tool::Tool;
-use gpui::{App, Task, WeakEntity, Window};
-use project::{ProjectPath, WorktreeId};
+use gpui::{App, Task, WeakEntity};
+use project::{Project, ProjectPath, WorktreeId};
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
-use workspace::Workspace;
 
 #[derive(Debug, Serialize, Deserialize, JsonSchema)]
 pub struct ReadFileToolInput {
@@ -38,12 +37,11 @@ impl Tool for ReadFileTool {
     fn run(
         self: Arc<Self>,
         input: serde_json::Value,
-        workspace: WeakEntity<Workspace>,
-        _window: &mut Window,
+        project: WeakEntity<Project>,
         cx: &mut App,
     ) -> Task<Result<String>> {
-        let Some(workspace) = workspace.upgrade() else {
-            return Task::ready(Err(anyhow!("workspace dropped")));
+        let Some(project) = project.upgrade() else {
+            return Task::ready(Err(anyhow!("project dropped")));
         };
 
         let input = match serde_json::from_value::<ReadFileToolInput>(input) {
@@ -51,7 +49,6 @@ impl Tool for ReadFileTool {
             Err(err) => return Task::ready(Err(anyhow!(err))),
         };
 
-        let project = workspace.read(cx).project().clone();
         let project_path = ProjectPath {
             worktree_id: WorktreeId::from_usize(input.worktree_id),
             path: input.path,