chore: adopt node-addon-landlock-run source as native/ subtree

Bring the node-addon-landlock-run tree (tag v0.0.1, commit 614f7fd) into
native/landlock-run as its source of record: launcher development happens
here, next to the harness consumers, and the standalone repository becomes
the release mirror the tree is exported to for packing and publishing
(procedure in native/README.md). The subtree keeps its own pnpm workspace
and lockfile and is NOT added to the harness workspace: harness installs,
gates, and CI never touch it. The mirror's .github/ stays out of the
subtree; a separate manually-dispatched workflow
(.github/workflows/landlock-run.yml) runs the subtree's CI legs — the
per-architecture native builds, real-kernel launcher proofs, and pack
rehearsal — adapted with working-directory/cache paths.

eslint ignores the subtree like vendor/; AGENTS.md gains the native/
layout line (+5 words on its budget ceiling).

eslint.config.mjs

@@ -13,6 +13,7 @@ export default tseslint.config(
       '.claude/**', // harness-local state (worktrees, skills) — other checkouts, not this one's sources
       '**/.doc-typecheck-*/**',
       'vendor/**', // vendored source keeps upstream style and idioms
+      'native/**', // imported landlock-run subtree: self-contained workspace with its own gates (native/README.md)
       '**/*.js',
       '**/*.mjs',
       '*.config.ts', // root tool configs (vitest, tsdown) — no project service