The byte-offset locator (AvroBinaryCursor) reached a PathStep kind it cannot resolve to a byte span — currently PathStep.Index: array elements sit inside length-prefixed blocks, so a single element's span is not graftable without rewriting the block framing. Surfaced only by sliceBytes / graftBytes; the decode-based surfaces (get / modify / at) keep supporting Index steps.
Human-readable diagnostic. Kept separate from toString so the default enum representation remains useful for structural inspection / pattern-matching-in-tests.
Human-readable diagnostic. Kept separate from toString so the default enum representation remains useful for structural inspection / pattern-matching-in-tests.