Record the two design decisions every Filament driver hook depends on, so the follow-up tickets do not each re-decide them:

• Correlated $lookup (let + pipeline) rather than localField/foreignField, which sets a MongoDB 5.0 floor for the hooks. This is the option PHPLARA-225 (PR #3560) declined for withCount because CI still covered 4.4; decide whether that floor is acceptable for the hooks only or for the package.
• Compare keys as strings on both sides ($toString) so string foreign keys match ObjectId _id values, the coercion gap named in PR #3560.

Filament features this enables: every table feature below that sorts or filters through a relationship (PHPLARA-281 and the orderByRelationAggregate / whereRelationAggregate / orderByRelation hooks). Filament calls the hooks only when the connection driver is not MySQL/MariaDB/Postgres/SQLite/SQL Server and the method exists on the builder (filamentphp/filament#20442).

Deliverable: a short decision note in the repo (AGENTS.md or docs), no code.