Clarify Deno Desktop serving docs around loopback reachability

The Deno Desktop serving docs say the server is always bound to loopback, even if `0.0.0.0` is passed to `Deno.serve()`:

https://docs.deno.com/runtime/desktop/serving/

That explains why it is not reachable from other machines, but the page also says other apps and other users on the same machine cannot reach it. That part seems stronger than loopback binding alone guarantees.

Could the docs clarify whether Deno Desktop only forces loopback binding, or whether there is additional local-process isolation involved?

Start with the Deno Desktop serving documentation at the linked page and compare its loopback-binding statement with its claim about access by other local apps and users. Verify whether Desktop adds process isolation beyond binding behavior. Done when the page accurately distinguishes remote reachability from same-machine reachability and explains the relevant limitation.

Written by the indexing model from the issue text.