refactor: organise source files by ownership

Separate host-independent helpers under common/core and colocate feature
support code with its owners. Update imports, tests, and source-layout
guidance while preserving runtime behaviour.

src/common/core/replication/resources/shared.ts

@@ -0,0 +1,24 @@
+import { createOwnedResource } from "octagonal-wheels/resource";
+import type { RemoteDBSettings } from "@vrtmrz/livesync-commonlib/compat/common/types";
+
+/**
+ * Closeable surface of a concrete Replicator owned by one private resource.
+ *
+ * It deliberately exposes no active-provider controls: the resource may use
+ * the helper for one bounded operation, then must dispose it without
+ * publishing or replacing the active Replicator.
+ */
+export interface ResourceReplicator {
+    closeReplication(): void | Promise<void>;
+}
+
+/** Create one idempotent asynchronous disposer for a private Replicator. */
+export function createReplicatorDisposer(replicator: ResourceReplicator): () => Promise<void> {
+    const resource = createOwnedResource(replicator, (owned) => Promise.resolve().then(() => owned.closeReplication()));
+    return () => Promise.resolve(resource.dispose());
+}
+
+/** Fence a finite resource from later edits to its source settings object. */
+export function snapshotRemoteSettings(setting: RemoteDBSettings): RemoteDBSettings {
+    return { ...setting };
+}