[Share] "Copy link" stuck loading when /short_url fails

Kibana version: main

Elasticsearch version:

Server OS version:

Browser version:

Browser OS version:

Original install method (e.g. download page, yum, from source, etc.):

Describe the bug: In Kibana’s share UI, if the /short_url request fails, the "Copy link" button stays stuck in a loading/disabled state and the user gets no feedback that something went wrong.

Steps to reproduce:

1. Open a Dashboard in Kibana
2. In DevTools, block requests to /short_url
3. Open Share and click Copy link
4. Observe the Copy button stuck in a loading/disabled state with no error feedback

Expected behavior: When /short_url fails, show a toast that a URL could not be generated, and leave the Copy link button clickable so the user can retry without closing the modal.

Screenshots (if relevant):

Errors in browser console (if relevant): N/A

Provide logs and/or server output (if relevant):

Any additional context: Reproduces on main.