fix(tasks): contain async completion listeners

TaskService contained synchronous listener throws but discarded returned promises. An async TaskDoneListener could therefore reject as an unhandled process rejection even though the API promises per-listener containment.

Allow listeners to return PromiseLike<void> and attach a rejection handler to each result without awaiting it. This logs asynchronous failures independently while preserving the observation-only contract: later listeners, task waiters, and teardown are not delayed. Add a regression test and synchronize the public docs and generated API declaration.

packages/cordis/tool-cordis/src/api-catalog.ts

@@ -939,7 +939,7 @@ export const TYPE_API: readonly TypeApiEntry[] = [
   },
   {
     name: 'TaskDoneListener',
-    declaration: 'export type TaskDoneListener = (snapshot: TaskSnapshot, owner: Agent | undefined) => void;',
+    declaration: 'export type TaskDoneListener = (snapshot: TaskSnapshot, owner: Agent | undefined) => void | PromiseLike<void>;',
   },
   {
     name: 'TaskHooks',