#5475 "Rule form: pick the host, then its part…". CI run 8909 caught it: moving from the whole host to a mount kept "CPU" in the mount's Metric list, because a chosen metric always stayed on offer. Only a rule's own page keeps its resource and metric after they go quiet (keep=True from edit_rule); the pickers' swaps drop a metric the new part doesn't report. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>