fix(test): update tracked-replace assertion to match word-diff behavior (#2851)

PR #2817 added word-level diffing so multi-word tracked replacements
fragment into per-word insert/delete pairs — "a tracked style" → "new
fancy" becomes two tracked changes ("a" → "new" around a preserved
space, then "tracked style" → "fancy"). The `getDocumentText()`
assertion in programmatic-tracked-change.spec.ts still expected the
pre-word-diff behaviour where "new fancy" appeared as one contiguous
string, which produced this on all three browsers:

  Expected substring: "new fancy"
  Received string:    "Here is anew tracked stylefancy change"

Assert the inserted words "new" and "fancy" each appear in the
document text instead, and leave a comment explaining the new
semantics so the next reader doesn't have to retrace this.

Ran tests/comments/programmatic-tracked-change.spec.ts in chromium
locally — all 5 cases pass.

Author: caio-pizzol

tests/behavior/tests/comments/programmatic-tracked-change.spec.ts

@@ -60,7 +60,12 @@ test('tracked replace via document-api', async ({ superdoc }) => {
   assertMutationSucceeded('replaceText', receipt);
   await superdoc.waitForStable();
 
-  await expect.poll(() => getDocumentText(superdoc.page)).toContain('new fancy');
+  // word-diff (PR #2817) fragments multi-word tracked replacements into per-word
+  // insert/delete pairs, so "new fancy" appears as two separate inserts around
+  // the surviving space token. Assert both inserted words are present rather
+  // than a contiguous substring, which was the pre-word-diff assumption.
+  await expect.poll(() => getDocumentText(superdoc.page)).toContain('new');
+  await expect.poll(() => getDocumentText(superdoc.page)).toContain('fancy');
   await assertTrackChangeTypeCount(superdoc, 'insert');
 
   await superdoc.snapshot('programmatic-tc-replaced');