test(vector): mock 对 dim<=0 不再除零（保持 dim0→ErrInvalidDim 意图）

internal/runtime/memory/vector/index_test.go

@@ -62,6 +62,10 @@ func (m *mockEmbedder) Embed(ctx context.Context, texts []string) ([]embedding.V
 	}
 	out := make([]embedding.Vector, len(texts))
 	for i := range texts {
+		if m.dim <= 0 {
+			out[i] = embedding.Vector{}
+			continue
+		}
 		v := make(embedding.Vector, m.dim)
 		v[i%m.dim] = 1
 		out[i] = v