[Lane 2 · native] NotImplemented stubs — gzip/tar extraction for MNIST and CIFAR-10 on native and browser targets #1424

Sub-issue of #1414 ([Feature]: Close the remaining NotImplemented stubs outside the operator surface).

Lane: 2 · Kotlin core
Skill needed: Kotlin Multiplatform; compression formats.
Size: m (1–2 days)
Blocked by: nothing

What to do

1. The MNIST / FashionMNIST / CIFAR-10 loaders in skainet-data/skainet-data-simple/src/{linux,macos,ios,js,wasmJs}Main/ reject .gz / .tar.gz because no inflater exists there.
2. Pick a KMP-compatible inflate implementation (a small pure-Kotlin inflater, or platform zlib via cinterop on native) and use it; document the choice in the PR.
3. Run the data module tests for the targets you can run.

Acceptance

• Compressed datasets load on at least linuxX64 and wasmJs
• Result reported back on the parent issue

Notes

If something here turns out to be wrong or much bigger than the size label, comment on this issue or open a specific bug instead of blocking the parent.

Coverage matrix: docs/modules/ROOT/pages/reference/ops-status-matrix.adoc · How lanes work: Issue taxonomy