Fix a duplicate node id in the relation graph. Requires source, the wrong id, and target, the canonical id to keep. Every edge mentioning the wrong id is rewritten to the right one. When both ids have the same live fact, the existing canonical edge wins and the duplicate is discarded; closed historical edges are only re-keyed, not deduplicated. Use it as soon as graph_search shows two ids for the same thing. Node ids are typed "type:id" strings such as person:alex or tech:vue; the optional graph parameter selects a namespace and defaults to "memory".
