assistant2: Add tool lists for each context server (#27029)

This PR updates the list of context servers with the ability to view the
tools provided by the context server:

<img width="1394" alt="Screenshot 2025-03-18 at 5 53 05 PM"
src="https://github.com/user-attachments/assets/4ffe93dd-f9e9-44e7-877f-656ebf45a326"
/>

Release Notes:

- N/A

crates/assistant2/src/thread_store.rs

@@ -69,6 +69,10 @@ impl ThreadStore {
         self.context_server_manager.clone()
     }
 
+    pub fn tools(&self) -> Arc<ToolWorkingSet> {
+        self.tools.clone()
+    }
+
     /// Returns the number of threads.
     pub fn thread_count(&self) -> usize {
         self.threads.len()