datalog: findall aggregate (159/159)

(findall L V Goal) — bind L to the distinct V values for which Goal
holds, or the empty list when none. One-line addition to
dl-do-aggregate that returns the unreduced list. Tests cover EDB,
derived relation, and empty cases.

Useful for "give me all the X such that ..." queries without
scalar reduction.

plans/datalog-on-sx.md

@@ -186,9 +186,10 @@ large graphs.
 
 ### Phase 8 — aggregation (Datalog+)
 - [x] `(count R V Goal)`, `(sum R V Goal)`, `(min R V Goal)`,
-      `(max R V Goal)` — first arg is the result variable, second is the
-      aggregated variable, third is the goal literal. Live in
-      `lib/datalog/aggregates.sx`.
+      `(max R V Goal)`, `(findall L V Goal)` — first arg is the result
+      variable, second is the aggregated variable, third is the goal
+      literal. `findall` returns the distinct-value list itself; the
+      others reduce. Live in `lib/datalog/aggregates.sx`.
 - [x] `dl-eval-aggregate`: runs `dl-find-bindings` on the goal under the
       current subst (which provides outer-context bindings), collects
       distinct values of the aggregated var, applies the aggregate.
@@ -269,6 +270,13 @@ large graphs.
 
 _Newest first._
 
+- 2026-05-08 — Phase 8 extension: `findall L V Goal` aggregate. Bind
+  L to the list of distinct V values for which Goal holds (or the
+  empty list when no matches). Implemented as a one-line case in
+  `dl-do-aggregate`. 3 new tests: EDB, derived relation, empty.
+  Useful for "give me all the X such that …" queries without
+  scalar reduction.
+
 - 2026-05-08 — Phase 5d semantic fix: anonymous `_` variables are
   renamed per occurrence at `dl-add-rule!` and `dl-query` time so
   `(p X _) (p _ Y)` no longer unifies the two `_`s. New helpers