False Positive: `Part A of..` -> `Part a of..` (`UseTitleCase`)

**What got flagged?**
`## Part A of the Parts` corrected to `## Part 1 a of the Parts` by `UseTitleCase`.

**Why is this incorrect?**
`A` is not being used as a preposition or a determiner - it is being used as a pronoun - and therefore should be capitalized.

**Example of correct usage:**
```md
## Part A of the Parts
```

The issue identifies the UseTitleCase rule and provides the incorrect and expected Markdown headings; locate that rule and its existing tests first. Add coverage showing that “A” in “Part A of the Parts” remains capitalized, then run the rule’s tests and confirm the heading is unchanged.

Written by the indexing model from the issue text.