list-my-actors: list the Actors of the account

[DaveHanns]

Problem

An agent cannot find out which Actors the account owns. search-actors searches Store, so private Actors never show up (#997), and the run list only reveals Actors that have run. Agents end up guessing names or calling the API directly. Item 1 of #1053; the maintainer asked for one issue per item there.

Proposal

A read-only list-my-actors tool wrapping GET /v2/acts?my=1 through client.actors().list({ my: true, limit, offset, desc, sortBy }). Returns id, name, username, createdAt, modifiedAt per Actor plus paging info; sortBy accepts createdAt or stats.lastRunStartedAt. Titles are not in the list endpoint, so an agent that needs them calls fetch-actor-details per Actor.

Notes

• No arguments required; defaults limit 20, newest first.
• The response should point at fetch-actor-details and push-actor when they are loaded.

Part of #1412.

Draft PR: #1434