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/now_tool.rs

@@ -3,7 +3,8 @@ use std::sync::Arc;
 use anyhow::{anyhow, Result};
 use assistant_tool::Tool;
 use chrono::{Local, Utc};
-use gpui::{App, Task, WeakEntity, Window};
+use gpui::{App, Task, WeakEntity};
+use project::Project;
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
 
@@ -41,8 +42,7 @@ impl Tool for NowTool {
     fn run(
         self: Arc<Self>,
         input: serde_json::Value,
-        _workspace: WeakEntity<workspace::Workspace>,
-        _window: &mut Window,
+        _project: WeakEntity<Project>,
         _cx: &mut App,
     ) -> Task<Result<String>> {
         let input: NowToolInput = match serde_json::from_value(input) {