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/.gitignore

@@ -0,0 +1,13 @@
+# Built native binaries ride npm tarballs via each package's `files` list,
+# never git. Root-level rules on purpose: a package-nested ignore file would
+# also steer `pnpm pack` and has silently dropped payload from tarballs before.
+packages/*/bin/
+packages/*/lib/
+
+/.claude/
+/.release/
+dist/
+node_modules/
+/package-lock.json
+*.log
+*.tsbuildinfo