Very slow when number of annotation is over 100

100-200 was arbitrarily chosen. In general the behaviour is getting very lagging after adding few dozens of annotations.

The annotation XML is 187KB.

No file, test, or entry point is named. Start by reproducing the lag with an annotation set containing a few dozen annotations and the reported 187KB XML, then compare behavior as annotations are added. Done means the annotation tool remains responsive beyond the reported range, with a regression check for large annotation files.

Written by the indexing model from the issue text.