[edalzell]

When Bard's value changes after a save, the editor was rebuilt with clearContent + setContent unless it was focused and only set values differed. The rebuild destroys every set NodeView, so nested fields lose their state, e.g. a Replicator with collapse: true inside a set re-reads meta.collapsed (which the save response resets) and an expanded set snaps shut. Reproduced by adding a Replicator row inside a Bard set and clicking Save.

Two kinds of diff now avoid the rebuild. Set-value-only differences (the response hands values back with keys reordered) are skipped regardless of focus, since sets already sync their own values into the editor. With remove_empty_nodes the response also lacks the empty paragraphs the editor still holds, so those are deleted in place with a transaction (mirroring Bard::removeEmptyNodes()), keeping a text selection so a set doesn't get node-selected and have its NodeView recreated by the decoration change.

Anything else still rebuilds, which keeps the #15440 fix. Persisting single-set collapse state to meta is #15688.

References #15687