assistant_tool: Add a source to the Tool trait (#26471)

This PR adds a `source` method to the `Tool` trait.

This will allow us to track where a tool is coming from.

Release Notes:

- N/A

crates/context_server/src/context_server_tool.rs

@@ -1,7 +1,7 @@
 use std::sync::Arc;
 
 use anyhow::{anyhow, bail, Result};
-use assistant_tool::Tool;
+use assistant_tool::{Tool, ToolSource};
 use gpui::{App, Entity, Task};
 use project::Project;
 
@@ -37,6 +37,12 @@ impl Tool for ContextServerTool {
         self.tool.description.clone().unwrap_or_default()
     }
 
+    fn source(&self) -> ToolSource {
+        ToolSource::ContextServer {
+            id: self.server_id.clone().into(),
+        }
+    }
+
     fn input_schema(&self) -> serde_json::Value {
         match &self.tool.input_schema {
             serde_json::Value::Null => {