Function plugin_state_get 

pub fn plugin_state_get(
    store: &Store,
    plugin_id: &str,
    grants: &[Permission],
    key: &str,
) -> Result<Value>

Namespaced plugin state (§23): get one key. Requires the calling plugin’s StateRead grant (checked by the host before dispatch; the engine re-checks here so direct invoke() callers are gated too).