Store SSH remote agent hosts in storage (#316796)

* Store SSH remote agent hosts in storage

Move SSH remote agent host connection details out of the user-visible remote agent hosts setting and into application storage. Keep WebSocket remote hosts in the setting and migrate legacy SSH entries on startup.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Address SSH remote storage review

Listen for SSH remote storage changes so configured entry removals notify consumers, update configuredEntries documentation, and add coverage for legacy SSH setting migration and storage-only removal events.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>