Require Applicative (g s) as a superclass of FieldGrammar

[Bodigrim]

I think we can finally act on the old TODO, cutting a bit of boilerplate.

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[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-05-17 21:01 UTC · Rule: default
• ✅ Checks passed · on draft merge queue: embarking master (67f85b0) and #11821 together #11847
• ✅ Merged — 2026-05-17 22:50 UTC · at 4e2cbec7f1cfda39cbc5a9c70f14c0e92e3eecba · merge

This pull request spent 1 hour 49 minutes 1 second in the queue, including 1 hour 38 minutes 2 seconds running CI.

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