High CPU utilisation using Obsidian plugin

**Describe the bug**
I'm running a relatively high-spec Asus with 8-core i7 and 24gb, but Harper is bumping CPU utilisation up noticeably (about 20% higher that usual).
I also note that the "squiggly" red underline for mis-spelled words is flickering, and suggested spelling tries but fails to overlay with that flieckering.

**Expected behavior**
No unnatural additional resource utilisation

**Platform**
Win11 Home, Obsidian v13.7, Harper 2.8.0

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Start by reproducing the issue on Windows 11 with Obsidian v13.7 and Harper 2.8.0, then profile CPU use while triggering the flickering red underlines and spelling suggestions. Done means the reported extra CPU utilisation is resolved and the overlays remain stable; the issue does not name a file or test to begin with.

Written by the indexing model from the issue text.