Add zed://extension/{id} links (#34492)

Release Notes:

- Add zed://extension/{id} links to open the extensions UI with a
specific extension

crates/agent_ui/src/agent_configuration.rs

@@ -491,6 +491,7 @@ impl AgentConfiguration {
                                         category_filter: Some(
                                             ExtensionCategoryFilter::ContextServers,
                                         ),
+                                        id: None,
                                     }
                                     .boxed_clone(),
                                     cx,

crates/agent_ui/src/agent_panel.rs

@@ -1921,6 +1921,7 @@ impl AgentPanel {
                                 category_filter: Some(
                                     zed_actions::ExtensionCategoryFilter::ContextServers,
                                 ),
+                                id: None,
                             }),
                         )
                         .action("Add Custom Server…", Box::new(AddContextServer))