chore: Add (currently failing) test for aggregates ignoring relationship limit

[sevenseacat]

An aggregate over a has_many that declares a limit counts/lists all related rows instead of the limited top-N. count(top_5_posts) should be bounded to 5.

Reproduction (failing test on main over the existing Comment.top_ratings, which is limit: 2, sort: [score: :desc]):

# aggregates on Comment:
count(:count_of_top_ratings, :top_ratings)
list(:top_rating_scores, :top_ratings, :score)

# create 5 ratings (scores 1..5), then:
assert %{count_of_top_ratings: 2, top_rating_scores: [5, 4]} = ...
# actual: count_of_top_ratings: 5, top_rating_scores: [5,4,3,2,1]

Root cause (ash_sql/lib/aggregate.ex): in get_subquery/… (the relationship-path clause), on_subquery runs select_all_aggregates (the GROUP BY + count/array_agg) before related_subquery calls limit_from_many (join.ex:397). So any limit is applied after grouping — it caps the number of groups, not rows-per-group. The generated SQL puts LIMIT after GROUP BY resource_id inside the lateral join.

What the fix needs: when the source relationship has limit/offset, the correlated+sorted rows must be wrapped in an inner … ORDER BY <rel.sort> LIMIT n subquery before the aggregate folds them:

SELECT resource_id, count(*)
FROM (SELECT * FROM comment_ratings WHERE <parent-corr> ORDER BY score DESC LIMIT 2) sc0
GROUP BY resource_id

Attempt / how far it got: gating on rel.limit, I passed sort?: true and split the default apply_relationship_subquery to build the inner correlated+ordered+limited subquery, then group outside. The inner subquery builds correctly (verified: parent_as correlation + ORDER BY score DESC + LIMIT). The blocker is composing the grouped outer level into the left_lateral_join — Ecto raises "invalid query was interpolated in a join"; the added nesting level needs the as/parent_as + start_bindings_at/current binding bookkeeping to be rebased, which the single-level aggregate path doesn't currently do.

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[zachdaniel]

This has been fixed in latest ash_sql