Snapshot-based undo/redo (max 50 steps) with Cmd+Z / Cmd+Shift+Z,
ignoring volatile generation progress fields. Bind the remaining
reference shortcuts: Cmd+D duplicate, Cmd+Enter generate selection,
Tab new-node palette, Cmd+F canvas node search panel, Cmd+0 fit view,
Cmd+=/- zoom, V pan-tool toggle, H hold-to-pan, plain G to group.
Expand the shortcut help panel to the full four-group layout.
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