Character count on fields via Maxlength integration (D9)

Problem/Motivation

Looking for a way to make Maxlength module work with description metatag field on per-node metatags.

Steps to reproduce

Have a client who:
A) Uses Maxlength module along with Text Summary Options on their body summary to require summary text with a soft limit of 160 chars
B) Uses body summary to populate the description metatag.
C) Exposes certain Metatag fields, like description metatag, on node edit forms to allow overrides.
D) Wants a consistent UI for the description metatag override field, with the maxlength module countdown indicator.

Effectively, they want to permit longer body summary text for teasers and card displays with the soft limit, but enforce a hard limit of 160 on the metatag override field.

Proposed resolution

My initial guess is that this is just a small hook_form_alter() away. But I haven't looked into maxlength module's form api integration yet. So I wanted to capture this support request here so others can either chime in with their recipe — if one exists — or we can discuss and document a solution.

Remaining tasks

User interface changes

API changes

Data model changes