GET /runs/{id}/nodes/{node}/outputs serves what a node returned

The stage cache's stored outputs, as kept (up to 256 kB of JSON). A node
that kept none answers 404 saying why. Listed in the API docs.

frontend/src/client/types.gen.ts

@@ -2162,6 +2162,15 @@ export type RunsDeleteRunData = {
 
 export type RunsDeleteRunResponse = (void);
 
+export type RunsReadNodeOutputsData = {
+    node: string;
+    runId: string;
+};
+
+export type RunsReadNodeOutputsResponse = (({
+    [key: string]: unknown;
+} | null));
+
 export type RunsCancelRunData = {
     runId: string;
 };