[Lane 2 · native] NotImplemented stubs — IRPA FileBacked transfer on Kotlin/Native #1423

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

Lane: 2 · Kotlin core
Skill needed: Kotlin/Native; POSIX mmap.
Size: m (1–2 days)
Blocked by: nothing

What to do

1. FileBackedTransfer.native.kt in skainet-io/skainet-io-iree-params/src/nativeMain/ throws NotImplementedError.
2. Implement it with mmap via cinterop (see how skainet-lang-core's native PlatformStorage maps files) and add a native test.
3. Delete the file's line from config/stub-allowlist.txt; run ./gradlew :skainet-io:skainet-io-iree-params:linuxX64Test checkUnmarkedStubs.

Acceptance

• Native targets read FileBacked IRPA parameters
• 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