Editing any field of a grouped node dropped it out of the group on the
next save. NodeModal validated the parent against the type rules
(proxmox/vm/lxc/docker_host) or `container_mode`, and a `group` node is
neither — so it cleared `parent_id` on submit, `updateNode` detached the
node and the save persisted `parent_id: null`.
A shared `isValidParentNode` now treats a group as a valid parent for
any child type; the type rules only govern container nesting. Two
siblings of the same bug go with it: `updateNode` and `addNode` only
nested under a `container_mode` parent, so assigning or adding a node to
a group left it visually unparented until the next reload.
ha-relevant: yes
Pouzor
26e18dafdd