fix: accept []string and []int in matrix refs (#2544)

[no-hup]

Fixes #2544.

Matrix ref: only accepted a literal []any, so a ref computed with a template function like splitList came back as []string and failed with "must resolve to a list" even though its a perfectly good list. trulede already pinned this down on the issue, the type switch just never matched.

The fix adds a small helper (resolvedAsAnySlice) that accepts []any, []string and []int. that set deliberately mirrors what itemsFromFor already takes for literal lists, so nothing that worked before behaves differently, no reflect involved. Enum refs shared the same []any assertion so they get the same widening.

Tests: a table test for the conversion (any/string/int slices plus two error cases) and an end-to-end fixture task loop-matrix-ref-computed that loops over a splitList ref, with a golden file. go test ./... is green locally.

Disclosure: I used an AI assistant to help implement and test this change. I've reviewed and verified it and I'm happy to explain or revise anything here.