Feature: add CLI command to close tweet compose window

[jackleeio]

Summary

Add a CLI command to close the tweet compose window / draft modal in the BNBot Chrome extension flow.

Problem

When using BNBot from OpenClaw/CLI in draftOnly mode, the compose window stays open after creating a draft. There is currently no dedicated command to dismiss or close the composer programmatically.

In practice this causes friction for agent workflows:

• the agent can create a draft successfully
• but cannot cleanly exit the compose UI afterward
• the human has to manually click X or press Esc

Requested feature

Add a command such as:

bnbot close-compose-window

or a more general UI action command that can dismiss the current compose modal/drawer when it is open.

Expected behavior

• If the tweet compose window is open, close it
• If a draft exists, preserve it unless explicitly told to discard
• Return structured JSON indicating whether a window was found and closed
• If no compose window is open, return a safe no-op result