remove unused second argument to source, and runtime immutable option to createRoot (not sure what that was doing there?)

packages/svelte/src/internal/client/render.js

@@ -2606,7 +2606,6 @@ export function spread_props(props) {
  * 		events?: Events;
  *  	context?: Map<any, any>;
  * 		intro?: boolean;
- * 		immutable?: boolean;
  * 		recover?: false;
  * 	}} options
  * @returns {Exports & { $destroy: () => void; $set: (props: Partial<Props>) => void; }}
@@ -2624,15 +2623,8 @@ export function createRoot(component, options) {
 	 * @param {any} value
 	 */
 	function add_prop(name, value) {
-		const prop = source(
-			value,
-			options.immutable
-				? /**
-				   * @param {any} a
-				   * @param {any} b
-				   */ (a, b) => a === b
-				: safe_equal
-		);
+		const prop = source(value);
+		prop.e = safe_equal; // TODO should this be default_equal?
 		_sources[name] = prop;
 		define_property(_props, name, {
 			get() {
@@ -2666,11 +2658,10 @@ export function createRoot(component, options) {
 			return _props[property];
 		}
 	});
-	const props_source = source(
-		props_proxy,
-		// We're resetting the same proxy instance for updates, therefore bypass equality checks
-		() => false
-	);
+	const props_source = source(props_proxy);
+
+	// We're resetting the same proxy instance for updates, therefore bypass equality checks
+	props_source.e = safe_equal;
 
 	let [accessors, $destroy] = mount(component, {
 		...options,

packages/svelte/src/internal/client/runtime.js

@@ -1142,25 +1142,20 @@ export function derived(init) {
 /**
  * @template V
  * @param {V} initial_value
- * @param {import('./types.js').EqualsFunctions<V>} [equals]
  * @returns {import('./types.js').SourceSignal<V>}
  */
 /*#__NO_SIDE_EFFECTS__*/
-export function source(initial_value, equals) {
+export function source(initial_value) {
 	const source = create_source_signal(SOURCE | CLEAN, initial_value);
 	source.x = current_component_context;
-	source.e = get_equals_method(equals);
+	source.e = get_equals_method();
 	return source;
 }
 
 /**
- * @param {import('./types.js').EqualsFunctions} [equals]
  * @returns {import('./types.js').EqualsFunctions}
  */
-function get_equals_method(equals) {
-	if (equals !== undefined) {
-		return equals;
-	}
+function get_equals_method() {
 	const context = current_component_context;
 	if (context && !context.i) {
 		return safe_equal;

packages/svelte/src/legacy/legacy-client.js

@@ -68,7 +68,6 @@ class Svelte4Component {
 			target: options.target,
 			props: { ...options.props, $$events: this.#events },
 			context: options.context,
-			immutable: options.immutable,
 			intro: options.intro,
 			recover: options.recover
 		});