fix: destroy each items after siblings are resumed (#17258)

* fix: destroy each items after siblings are resumed * changeset * remove unused exports * tidy up * fix: correctly reconcile each blocks after outroing branches are resumed * WIP * add some logging * fix * remove item on destroy * remove * remove * WIP * WIP * WIP * WIP * WIP * WIP * WIP * WIP * WIP * WIP * WIP * WIP * WIP * tests passing * tidy up * tidy up * note to self * tidy up * fix * add stress test to repo

Author: Rich-Harris

.changeset/flat-cars-say.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: correctly reconcile each blocks after outroing branches are resumed

.changeset/great-bikes-listen.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: destroy each items after siblings are resumed

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

@@ -40,6 +40,7 @@ export const EAGER_EFFECT = 1 << 17;
 export const HEAD_EFFECT = 1 << 18;
 export const EFFECT_PRESERVED = 1 << 19;
 export const USER_EFFECT = 1 << 20;
+export const EFFECT_OFFSCREEN = 1 << 25;
 
 // Flags exclusive to deriveds
 /**