[False Positive] `Apr` -> `APR` when used as abbreviated month

**What got flagged?**
```md
Apr 1st
```

`Apr` was flagged with: `This word's canonical spelling is all-caps. (Harper OrthographicConsistency)`

**Why is this incorrect?**
The correct capitalization of month abbreviation is to only capitalize the first letter. Harper does not give this hint for other month abbreviations.

**Example of correct usage:**
```md
- Apr 1st: April fools day.
```

Reproduce the false positive with `Apr 1st` and trace the `Harper OrthographicConsistency` rule that reports it. Done means the normal month abbreviation capitalization is accepted, while the existing behavior for other month abbreviations remains unchanged.

Written by the indexing model from the issue text.