refactor!: upgrade cosmoz dependencies + simplify IonReader API - #2

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

function `strip_ansi` is never used

function `strip_ansi` is never used

function `ion_fixture` is never used

function `read_bytes_to_tempfile_copy` is never used

function `mzml_fixture` is never used