Function handle_document_open 

pub async fn handle_document_open(
    uri: Uri,
    content: String,
    state: Arc<ServerState>,
    client: Client,
    config: Arc<RwLock<DepsConfig>>,
) -> Result<JoinHandle<()>>

Generic document open handler using ecosystem registry.

Parses manifest using the ecosystem’s parser, creates document state, and spawns a background task to fetch version information from the registry.