Adds host_agent/skill_sync.py (HostAgentSkillSync) which constructs the synced + local skill stores, the Cloud API sync client, and the runner, then drives them on the host-agent lifecycle: incremental per-host pull into the synced catalog, fork-on-revocation, and a best-effort local- skill inventory report to the Cloud (design D7). Wired into create_application + run_async start/stop. Host-agent suite green (219 passed). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>