[web/document-updater] display preview for accepted/rejected tracked changes (#36240)

* [web] add preview payload to track-change notification types

* [doc-updater] pass accepted/rejected change data through to web for previews

* [web] snapshot change preview onto accepted/rejected notifications

* [web] render resolved change previews instead of accepted/rejected count lines

* [web] add unit coverage for accepted/rejected change preview flow

* fix: notification carries multiple previews per accept/reject batch; extract shared group helper

* fix: one preview per accept/reject action, drop adjacency grouping

* fix: move buildResolvedChangePreviews out of the email builder class

* fix: type error, make tests more explicit

* fix: render resolver below preview

* fix: overflow text, alignment

* fix: test error

* fix: resolved count

* [document-updater/web] send sparse change preview instead of full doc lines

* fix: store sparse preview, hydrate at render, drop CE gate

* fix: advance slice cursor past tracked-delete text in sparse preview

* fix: inline buildChangeGroupPreview

* fix: changePreviewBuilder -> sparseChangePreview

* fix: rm change_contributors

* fix: copilot flagged testing issues

* fix: hydrate and truncate change preview at write time

* fix: avoid materializing full doc text when slicing preview window

* fix: update reject preview test to hydrated shape

* fix: accepted delete removing context

* [document-updater/web] split resolved change previews into one per change cluster

* fix: narrow cluster userIds to string[] for typecheck

* feat: updating to use zod schema for previews

---------

Co-authored-by: Jimmy Domagala-Tang <jimmy.domagala-tang@overleaf.com>
GitOrigin-RevId: 0740713c715a61a220180f353e497b27da6a5b0f

services/document-updater/app/js/HttpController.js

@@ -513,7 +513,7 @@ async function acceptChanges(req, res) {
     `accepting ${changeIds.length} changes via http`
   )
   const timer = new Metrics.Timer('http.acceptChanges')
-  const changeContributors =
+  const { changeContributors, previews } =
     await DocumentManager.promises.acceptChangesWithLock(
       projectId,
       docId,
@@ -525,7 +525,7 @@ async function acceptChanges(req, res) {
     `accepted ${changeIds.length} changes via http`
   )
 
-  res.status(200).json({ changeContributors })
+  res.status(200).json({ changeContributors, previews })
 }
 
 const commentWithUserSchema = z.object({