```python
def plan(rows, budget_cents, excluded_channels=()):
    if isinstance(budget_cents, bool) or not isinstance(budget_cents, int):
        raise ValueError("budget_cents must be a nonnegative integer")
    if budget_cents < 0:
        raise ValueError("budget_cents must be a nonnegative integer")

    normalized_excluded = {
        channel.strip().casefold() for channel in excluded_channels
    }

    seen_ids = set()
    candidates = []

    for row in rows:
        row_id = row["id"]
        if row_id in seen_ids:
            continue
        seen_ids.add(row_id)

        if row.get("archived", False):
            continue

        channel = row.get("channel", "")
        if channel.strip().casefold() in normalized_excluded:
            continue

        candidates.append(row)

    ordered_candidates = sorted(
        candidates,
        key=lambda row: row.get("priority", 0),
        reverse=True,
    )

    selected_ids = []
    spent_cents = 0
    remaining_cents = budget_cents

    for row in ordered_candidates:
        cost_cents = row["cost_cents"]
        if cost_cents <= remaining_cents:
            selected_ids.append(row["id"])
            spent_cents += cost_cents
            remaining_cents -= cost_cents

    return {
        "selected_ids": selected_ids,
        "spent_cents": spent_cents,
        "remaining_cents": remaining_cents,
    }
```