```python
def line_clusters(stops: list[str], links: list[tuple[str, str]]) -> list[list[str]]:
    if not stops:
        return []

    from collections import defaultdict, deque

    graph = defaultdict(list)
    for u, v in links:
        graph[u].append(v)
        graph[v].append(u)

    visited = set()
    clusters = []

    for stop in stops:
        if stop not in visited:
            cluster = []
            queue = deque([stop])
            while queue:
                current = queue.popleft()
                if current not in visited:
                    visited.add(current)
                    cluster.append(current)
                    for neighbor in graph[current]:
                        queue.append(neighbor)
            clusters.append(sorted(cluster))

    return sorted(clusters)
```