Feature request: onBeforeChange hook to intercept and optionally reject writes

[AleksY1991]

Problem:

Building apps with confirmation dialogs for destructive operations (bulk delete, mass updates). Currently:

1. Change happens → onChange fires
2. Show confirmation dialog
3. If rejected → manually rollback to previous state

This is fragile because:

• Other listeners already reacted to the change
• Computed values recalculated unnecessarily
• UI flickers (change → rollback)
• Race conditions if user makes another change during dialog

Use case:
// User selects 50 nodes and clicks "Delete"
// Want to: intercept → show "Delete 50 nodes?" → allow/reject

Proposed solution:
store$.nodes.onBeforeChange(async ({ changes, value, prev }) => {
if (changes.length > 5) {
const confirmed = await showConfirmDialog(Update ${changes.length} items?);
if (!confirmed) {
return false; // Reject - change doesn't happen
}
}
return true; // Allow
});