feat: Flag unnecessary do-past-tenses

## Description

It's quite common in English from non-native speakers who speak some European languages to unnecessarily use "did" in past tense constructions. For example: Which PDP-8 boot process variations **did exist**? → Which PDP-8 boot process variations **existed**?

## Resources

I'll keep me eye open for any discussion of this. Might exist on sites that list common mistakes for ESL students.

## Examples

Will start a list with the one I used in the description:
- Which PDP-8 boot process variations **did exist**? → Which PDP-8 boot process variations **existed**?

No implementation files, tests, or entry points are named in the issue. Start by locating existing grammar rules for unnecessary auxiliary verbs and their tests, then compare the reported “did exist” example. The work is done when that construction is flagged as unnecessary.

Written by the indexing model from the issue text.