```python
def drain_frames(chunks: list, marker: str) -> dict:
    if not isinstance(marker, str) or len(marker) != 1:
        raise ValueError("marker must be a single character")
    buffer = "".join(chunks)
    pending = ""
    frames = []
    for char in buffer:
        if char == marker:
            if pending:
                frames.append(pending)
                pending = ""
            if char == marker:
                pending += char
        else:
            pending += char
    if pending:
        frames.append(pending)
    return {"frames": frames, "pending": pending}
```