[ty] Warn users if server received unknown options (#19779)

## Summary

This PR updates the client settings handling to recognize unknown
options provided by the user and show a warning popup along with a
warning log message.

## Test Plan

Add E2E tests.

crates/ty_server/src/server.rs

@@ -98,6 +98,15 @@ impl Server {
         let (main_loop_sender, main_loop_receiver) = crossbeam::channel::bounded(32);
         let client = Client::new(main_loop_sender.clone(), connection.sender.clone());
 
+        if !initialization_options.options.unknown.is_empty() {
+            let options = serde_json::to_string_pretty(&initialization_options.options.unknown)
+                .unwrap_or_else(|_| "<invalid JSON>".to_string());
+            tracing::warn!("Received unknown options during initialization: {options}");
+            client.show_warning_message(format_args!(
+                "Received unknown options during initialization: {options}"
+            ));
+        }
+
         // Get workspace URLs without settings - settings will come from workspace/configuration
         let workspace_urls = workspace_folders
             .filter(|folders| !folders.is_empty())

crates/ty_server/src/session.rs

@@ -450,12 +450,23 @@ impl Session {
 
             // Combine the global options specified during initialization with the
             // workspace-specific options to create the final workspace options.
-            let ClientOptions { global, workspace } = self
+            let ClientOptions {
+                global, workspace, ..
+            } = self
                 .initialization_options
                 .options
                 .clone()
                 .combine(options.clone());
 
+            if !options.unknown.is_empty() {
+                let options = serde_json::to_string_pretty(&options.unknown)
+                    .unwrap_or_else(|_| "<invalid JSON>".to_string());
+                tracing::warn!("Received unknown options for workspace `{url}`: {options}");
+                client.show_warning_message(format!(
+                    "Received unknown options for workspace `{url}`: {options}",
+                ));
+            }
+
             combined_global_options.combine_with(Some(global));
 
             let workspace_settings = workspace.into_settings();

crates/ty_server/src/session/options.rs

@@ -1,3 +1,5 @@
+use std::collections::HashMap;
+
 use lsp_types::Url;
 use ruff_db::system::SystemPathBuf;
 use ruff_macros::Combine;
@@ -84,6 +86,11 @@ pub struct ClientOptions {
 
     #[serde(flatten)]
     pub(crate) workspace: WorkspaceOptions,
+
+    /// Additional options that aren't valid as per the schema but we accept it to provide better
+    /// error message to the user.
+    #[serde(flatten)]
+    pub(crate) unknown: HashMap<String, Value>,
 }
 
 impl ClientOptions {
@@ -98,6 +105,12 @@ impl ClientOptions {
         self.workspace.disable_language_services = Some(disable_language_services);
         self
     }
+
+    #[must_use]
+    pub fn with_unknown(mut self, unknown: HashMap<String, Value>) -> Self {
+        self.unknown = unknown;
+        self
+    }
 }
 
 /// Options that are global to the language server.