The demo.consul.io site is down

### Overview of the Issue

The [consul README](https://github.com/hashicorp/consul/blob/7054efd3cb64b02b045c8330da868e12c5e20b49/README.md?plain=1#L41) advertises a demo of Consul's web UI at https://demo.consul.io. That site is not currently reachable.

### Reproduction Steps

1. Get curious about Consul.
1. Visit https://github.com/hashicorp/consul.
1. Wonder what the what UI looks like and click the link in the README.
1. See "demo.consul.io’s server IP address could not be found."

### Describe the solution you'd like

Bring back the demo web UI and/or update the link :)

### Consul Version

n/a

### Browser and Operating system details

Chrome on Chrome OS

### Screengrabs / Web Inspector logs

```
$ dig demo.consul.io

; <<>> DiG 9.18.44-1~deb12u1-Debian <<>> demo.consul.io
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 49866
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;demo.consul.io. IN A

;; AUTHORITY SECTION:
consul.io. 589 IN SOA ns-1815.awsdns-34.co.uk. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400

;; Query time: 0 msec
;; SERVER: 100.115.92.193#53(100.115.92.193) (UDP)
;; WHEN: Mon Feb 23 21:36:22 PST 2026
;; MSG SIZE rcvd: 139
```

Start with the Consul README section linked in the issue and verify the current DNS status of demo.consul.io. Check whether the demo can be restored or whether the README should point elsewhere; done means the advertised link works or the dead link is removed or replaced.

Written by the indexing model from the issue text.