```python
"""The cheapest set of travel passes covering every trip day."""


def _validate_plan(trip_days, passes):
    for day in trip_days:
        if isinstance(day, bool) or not isinstance(day, int) or day < 1:
            raise ValueError("trip days must be positive integers")
    for earlier, later in zip(trip_days, trip_days[1:]):
        if later <= earlier:
            raise ValueError("trip days must be strictly increasing")
    if not passes:
        raise ValueError("at least one pass kind is required")
    for cover in passes:
        span = cover["span"]
        cost = cover["cost"]
        if isinstance(span, bool) or not isinstance(span, int) or span < 1:
            raise ValueError("pass span must be a positive integer")
        if isinstance(cost, bool) or not isinstance(cost, int) or cost < 0:
            raise ValueError("pass cost must be a non-negative integer")


def cheapest_pass_plan(trip_days: list, passes: list) -> dict:
    _validate_plan(trip_days, passes)
    
    n = len(trip_days)
    dp = [[float('inf')] * (n + 1) for _ in range(n + 1)]
    dp[0][0] = 0
    
    for i in range(1, n + 1):
        for j in range(i, n + 1):
            dp[i][j] = dp[i - 1][j]
            for pass_ in passes:
                if trip_days[j - 1] - trip_days[i - 1] < pass_["span"]:
                    continue
                dp[i][j] = min(dp[i][j], dp[i - pass_["span"]][i - 1] + pass_["cost"])
    
    if dp[1][n] == float('inf'):
        raise ValueError("no valid pass plan found")
    
    purchases = []
    i, j = n, n
    while i > 0:
        for pass_ in passes:
            if trip_days[j - 1] - trip_days[i - 1] < pass_["span"]:
                continue
            if dp[i][j] == dp[i - pass_["span"]][i - 1] + pass_["cost"]:
                purchases.append([trip_days[i - pass_["span"]], pass_["span"]])
                i -= pass_["span"]
                j = i + pass_["span"]
                break
    
    return {"total": dp[1][n], "purchases": purchases}
```