feat(ql3): establish 3.0 incubation baseline

back/runtime/ports/runDispatchCandidateSource.ts

@@ -0,0 +1,16 @@
+import type {
+  RunDispatchCandidate,
+  RunDispatchCandidateCursor,
+} from '../domain/runDispatchCandidate';
+
+export interface ListRunDispatchCandidatesOptions {
+  observedAtMs: number;
+  after?: RunDispatchCandidateCursor;
+  limit?: number;
+}
+
+export interface RunDispatchCandidateSource {
+  listCandidates(
+    options: ListRunDispatchCandidatesOptions,
+  ): Promise<RunDispatchCandidate[]>;
+}