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).

native/landlock-run/packages/linux-x64/package.json

@@ -0,0 +1,26 @@
+{
+  "name": "node-addon-landlock-run-linux-x64",
+  "version": "0.0.1",
+  "description": "Prebuilt landlock-run Landlock launcher binary for linux-x64 (static musl) — resolved as a file path by node-addon-landlock-run, never imported",
+  "os": [
+    "linux"
+  ],
+  "cpu": [
+    "x64"
+  ],
+  "files": [
+    "README.md",
+    "bin/",
+    "prebuilds.json"
+  ],
+  "scripts": {
+    "prepack": "node ../../scripts/verify-launcher-binary.mjs"
+  },
+  "engines": {
+    "node": ">=20"
+  },
+  "license": "BSD-3-Clause",
+  "publishConfig": {
+    "access": "public"
+  }
+}