use $state.eager mechanism for $effect.pending - way simpler and more robust

packages/svelte/src/compiler/phases/3-transform/client/visitors/CallExpression.js

@@ -80,7 +80,7 @@ export function CallExpression(node, context) {
 			);
 
 		case '$effect.pending':
-			return b.call('$.pending');
+			return b.call('$.eager', b.thunk(b.call('$.pending')));
 
 		case '$inspect':
 		case '$inspect().with':

packages/svelte/src/internal/client/dom/blocks/boundary.js

@@ -34,7 +34,7 @@ import { queue_micro_task } from '../task.js';
 import * as e from '../../errors.js';
 import * as w from '../../warnings.js';
 import { DEV } from 'esm-env';
-import { Batch, effect_pending_updates } from '../../reactivity/batch.js';
+import { Batch } from '../../reactivity/batch.js';
 import { internal_set, source } from '../../reactivity/sources.js';
 import { tag } from '../../dev/tracing.js';
 import { createSubscriber } from '../../../../reactivity/create-subscriber.js';
@@ -110,12 +110,6 @@ export class Boundary {
 	 */
 	#effect_pending = null;
 
-	#effect_pending_update = () => {
-		if (this.#effect_pending) {
-			internal_set(this.#effect_pending, this.#local_pending_count);
-		}
-	};
-
 	#effect_pending_subscriber = createSubscriber(() => {
 		this.#effect_pending = source(this.#local_pending_count);
 
@@ -329,7 +323,10 @@ export class Boundary {
 		this.#update_pending_count(d);
 
 		this.#local_pending_count += d;
-		effect_pending_updates.add(this.#effect_pending_update);
+
+		if (this.#effect_pending) {
+			internal_set(this.#effect_pending, this.#local_pending_count);
+		}
 	}
 
 	get_effect_pending() {

packages/svelte/src/internal/client/reactivity/batch.js

@@ -74,9 +74,6 @@ export let previous_batch = null;
  */
 export let batch_values = null;
 
-/** @type {Set<() => void>} */
-export let effect_pending_updates = new Set();
-
 /** @type {Effect[]} */
 let queued_root_effects = [];
 
@@ -324,16 +321,6 @@ export class Batch {
 		}
 
 		this.deactivate();
-
-		for (const update of effect_pending_updates) {
-			effect_pending_updates.delete(update);
-			update();
-
-			if (current_batch !== null) {
-				// only do one at a time
-				break;
-			}
-		}
 	}
 
 	discard() {