Approve phased Kotlin/Native + KMP support along this roadmap

[cgruber]

Child of #1682 (Kotlin/Native + KMP synthesis + prototype). Type: approval / governance.

This is the go/no-go. The anchor lays out the prior art, a working prototype (hermetic klib
compilation + cross-compiled native binaries, no JVM), and a phased plan (P1–P8). Before I
start landing PRs I'd like maintainer sign-off on two things:

1. Direction. Adopt phased Native/KMP support as described in the anchor's Section 5,
   driven as the implementation of @restingbull's [kmp] Outline of a roadmap #1466 roadmap: I'll rebase the prototype
   onto [kmp] Outline of a roadmap #1466's conventions (DirectoryInfo for konan.home, the reproducibility flags, its
   phase boundaries) rather than run a parallel branch.
2. First increment. Anchor the series on a hermetic, source-only kt_native_library
   (P1 toolchain foundation + P2 klib rule; no external deps, no expect/actual) as the
   first reviewable PR, with everything else sequenced behind it.

Asking for: 👍 on the direction and on the first-increment scope (or a counter). The
specific shape/naming/linking decisions are their own children (this issue doesn't need to
resolve them); it just needs agreement that this is worth doing along these lines.

[restingbull]

Need some more clarity on how the repository is structured and configured for different architecture/os requirements. The "use --platforms" leave a vast gap in the API surface that needs a little clarity.

Otherwise, the approach seems inline.