Fix the plan total check for a dashboard query

You asked an AI for a SQL query that counts active users per plan over the last 30 days, and it gave you one with a JOIN and a GROUP BY. Before execs read the numbers on a dashboard, your team checks that the per-plan counts add up to an independently counted total.

An assistant wrote reconcile_plan_totals(plan_counts, independent_total). It is in the editor. It has a bug. Find it and fix it.

Input and output:

• plan_counts: the query's count for each plan.
• independent_total: the number of active users counted another way, straight from the users table.
• Return "match", "fan_out:<n>", "dropped:<n>" or "invalid".

Rules the tests check:

• "invalid" when independent_total or any plan count is negative.
• Otherwise add up the plan counts. An empty list adds up to 0.
• "match" when the sum equals independent_total.
• "fan_out:<n>" when the sum is larger, where <n> is how much larger. Users were counted more than once.
• "dropped:<n>" when the sum is smaller, where <n> is how much smaller. Users went missing from the join.