arrowbricks v5.0.3

• Internal cleanup, no behavior change: the 21 hand-built permanent
  ApiError literals now use ApiError::permanent; the multi-frame LZ4
  decode loop (with its past silent-truncation fix) lives in one helper
  shared by the chunk-download and Thrift inline-blob paths; Cursor
  shares one schema-refresh helper and no longer copies the row list when
  nothing is buffered in fetchall()/fetchmany().