os-usque 0.2_18

Updates the bundled usque-nativetun port to upstream 0.8.2. The running binary version is now reported in Cloudflare request headers and truthful device telemetry instead of retaining an older registration-time client version. Existing egress client, Mesh node, legacy enrollment, and Access service-token enrollment behavior is preserved. Validation: 38 plugin unit tests, FreeBSD stage-qa, check-plist, release build, and package metadata checks.