Highlight word selection: Does not work when reselecting the same word

### What Happened?

Selected a word - others were highlighted. Then clicked elsewhere in the doc so the selection (and highlighting) was lost. Reselected the same word - no highlighting occurred. Selected a different word - highlighting occurred.

### Steps to Reproduce

1. Open a doc with multiple occurrences of a word
2. Turn on word highlighting plugin
3. Select target word
4. Deselect by clicking elsewhere
5. Reselect target word
6. Observe that highlighting no longer occurs.

### Expected Behavior

Highlighting of other occurrences of selected word happens regardless of past actions.

### OS Version

7.x (Horus)

### Session Type

Classic Session (X11, This is the default)

### Software Version

Latest release (I have run all updates)

### Log Output

_No response_

### Hardware Info

_No response_

首先，在启用单词高亮插件的情况下，在包含重复单词的文档中复现选择和取消选择的操作序列。跟踪插件对选择变化的处理，并将第一次选择与重新选择同一个单词进行比较。当焦点移到其他位置后，再次选择同一个单词能够高亮显示它的其他出现位置时，即表示完成。

由索引模型根据 Issue 内容生成。