ALL CAPS text causes weird diagnostics

## Description

example in screenshot


All caps version of the text causes harper to want to incorrectly replace "A" with "An"

Start by reproducing the all-caps example from the attached screenshot and inspect where Harper generates the diagnostic that replaces “A” with “An.” The issue names no source files or tests; done means the all-caps text no longer receives this incorrect replacement while normal diagnostics still work.

Written by the indexing model from the issue text.