fix(agents): don't trigger a full sync when deleting a single agent (#879) (#889)

Deleting a single agent from the agents list emitted `delete`, which the parent view wired to `syncAgents()` — firing a full `POST /agents/sync` against Wazuh and Velociraptor and then re-fetching. In environments with thousands of agents that full sync is slow and unnecessary; the backend DELETE endpoint already removes the agent from Wazuh, Velociraptor, and the database directly. Wire the single-delete event to `getAgents()` instead, so it just re-fetches the list — matching the existing bulk-delete path (onBulkDeleteComplete). The explicit toolbar "Sync" button still calls syncAgents() for users who want a full reconciliation. Fixes #879 Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>