Feature request: scheduled message sending (im +messages-send --send-at)

Feature request

Support scheduling a message to be sent at a specified future time, e.g.:

lark-cli im +messages-send --chat-id oc_xxx --markdown "..." --send-at "2026-09-11T11:00:00+08:00"

Context

• The Feishu/Lark client already supports scheduled sending (right-click the send button), but this capability is not exposed in the OpenAPI message module (checked llms-messaging.txt: send/reply/edit/forward/recall/batch APIs only, no scheduled/delayed send).
• Typical use case: weekly report messages that must land in a group chat at a fixed meeting time (e.g. Friday 11:00), prepared in advance by an agent/script.

Possible directions

1. Push for the OpenAPI to expose the client's scheduled-send capability, then wrap it in the CLI.
2. Or provide a CLI-side fallback (local scheduler / daemon) with idempotency, so agents can safely schedule one-shot sends.

Thanks!

Start with the im +messages-send command and compare the available message APIs in llms-messaging.txt with Lark's OpenAPI documentation. Determine whether scheduled sending is exposed; if it is not, the scope must first resolve the proposed local-scheduler fallback, including idempotency. Done means the chosen approach can schedule a one-shot message for the requested time and is exposed through the CLI.