First implementation (#1)

Reviewed-on: #1

fixtures/records/anchor-span.json

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+{"doc":"hale2026harmonic-damb","format":"scienting-anchor/1","kind":"sentence","node":"hca6dc5","node_hash":"8cfed5a34aab28517e89e8a164f0f96c14361de83ebc800439116e83ef479f34","own_hash":"c270571517825ceed31ca912b80ac76203effe47f1c84f8ee8962800d0afc92f","quote":{"exact":"first test case","prefix":"Water, H$_2$O, served as the ","suffix":", with a bending band near 1595 "},"rev":12,"span":[29,44],"store":"smithlab"}