MCP tools should return the item's public URL (content_get / content_list / content_publish)

[htdtkshi]

Summary

When creating and publishing content through the MCP server (content_create,
content_publish, content_get, content_list), none of the responses include
the item's public URL. The only identifying fields returned are collection
and slug.

Problem

To get the live URL of a published item today, you have to:

1. Know the site's base URL out-of-band (it's not returned by settings_get
   either, unless explicitly configured).
2. Manually guess/construct the path convention (e.g. /{collection}/{slug}),
   which may not hold for all collections (e.g. pages vs posts) or custom
   routing.

This makes it hard to script downstream automation — e.g. an agent that
publishes a post via MCP and then wants to hand the URL to a social scheduling
tool (Postiz, Buffer, etc.) has no reliable way to get it without a human
checking the admin UI first.

Proposal

• Include a computed url (absolute) or path (relative) field in the item
  object returned by content_create, content_update, content_publish,
  content_get, and content_list, when the item is published and the site
  base URL is configured.
• If the site base URL (settings.url) is unset, consider surfacing that
  clearly (e.g. a null url with a note) rather than silently omitting it.

Context

Ran into this while testing MCP integration end-to-end: created a post,
published it, and had no way to get its public URL back through MCP — had to
open the admin UI and copy it from the browser address bar.