[verified] refactor: establish service and frontend boundaries

public/state/request-coordinator.js

@@ -0,0 +1,14 @@
+export class RequestCoordinator {
+  #versions = new Map()
+  async run(channel, ownerId, operation) {
+    const version = (this.#versions.get(channel) || 0) + 1
+    this.#versions.set(channel, version)
+    try {
+      const value = await operation()
+      return { accepted: this.#versions.get(channel) === version, ownerId, value }
+    } catch (error) {
+      return { accepted: this.#versions.get(channel) === version, ownerId, error }
+    }
+  }
+  invalidate(channel) { this.#versions.set(channel, (this.#versions.get(channel) || 0) + 1) }
+}