Docs: clarify whether /goal is supported in the Claude Code desktop app

Summary

The /goal command was introduced in 2.1.139 and is documented at
https://code.claude.com/docs/en/goal.md. The docs list three supported
surfaces — interactive CLI, -p print mode, and Remote Control mode —
but the Claude Code desktop app (Mac/Windows) is not mentioned.

Question

Is /goal intended to work in the desktop app? If yes, please add it
to the supported-surfaces list in goal.md. If no, please state that
explicitly so users don't try it on an unsupported surface.

Context

• /goal is powered by the hooks system and requires the workspace

trust dialog to be accepted.

• It's unclear whether the desktop app initializes hooks and the trust

dialog the same way the CLI does.

• Version observed: 2.1.141

Suggested fix

Add an explicit "Supported surfaces" or "Availability" section to
https://code.claude.com/docs/en/goal.md naming every surface where
/goal is (or isn't) supported, including the desktop app.