App code reads input connectivity through node.isInputConnected /
node.getInputLink or the new slotLinks input helpers (inputHasLink,
inputLinkId, inputLink) instead of the input.link mirror. Serialized
operators (litegraphUtil compression, migrateReroute, linkFixer) and the
mirror-carried association shuffles (dynamicWidgets autogrow,
fixLinkInputSlots, useNodeReplacement transplant writes) stay on the
mirror until it is deleted.