fix: read batch-local array on each-block commit (#18879)

Another extraction from #18861 which I'm pretty sure you can also
construct a buggy reproduction for today, but with #18861 it's strictly
necessary so we don't need to come up with one now

.changeset/short-radios-sneeze.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: read batch-local array on each-block commit

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

@@ -216,9 +216,6 @@ export function each(node, flags, get_collection, get_key, render_fn, fallback_f
 		tag(each_array, '{#each ...}');
 	}
 
-	/** @type {V[]} */
-	var array;
-
 	/** @type {Map<Batch, Set<any>>} */
 	var pending = new Map();
 
@@ -234,6 +231,11 @@ export function each(node, flags, get_collection, get_key, render_fn, fallback_f
 
 		state.pending.delete(batch);
 
+		// The effect doesn't necessarily re-run in a batch right before that batch commits
+		// (its view of the collection may not have changed), so we read the collection
+		// as the committing batch sees it rather than using the most recent block run's result
+		var array = get(each_array);
+
 		state.fallback = fallback;
 		reconcile(state, array, anchor, flags, get_key);
 
@@ -264,7 +266,7 @@ export function each(node, flags, get_collection, get_key, render_fn, fallback_f
 	}
 
 	var effect = block(() => {
-		array = /** @type {V[]} */ (get(each_array));
+		var array = /** @type {V[]} */ (get(each_array));
 		var length = array.length;
 
 		/** `true` if there was a hydration mismatch. Needs to be a `let` or else it isn't treeshaken out */