deprecate `api webhook`

[lmb]

Seems like claude will try to use api webhook to interact with the API instead of the more user friendly commands. This is a problem because api webhook has a lot less validation, by design / necessity.

I think it's not worth investing more into this. If someone needs raw API access they can use the soon to be published openAPI spec and/or curl.

cc @carlsverre

[carlsverre]

@lmb if you can't think of any reason to keep it (I can't) remove it. otherwise hide it? but probably best to just kill it.