Plan a Meta budget reallocation

Compares the ad sets in a campaign (or the whole account) on cost per result — or ROAS where revenue exists — and produces a reallocation plan: which budgets to raise, which to lower, by how much, and why. Use when: the user asks where to put more money, or wants a defensible weekly rebalance. Do not expect it to write anything. It returns a plan; each move is then a separate meta_update_adset_budget call the user approves. Do not apply moves to an ad set still in the learning phase — the plan leaves those out and says so, because a budget change restarts learning. Do not exceed the step size without saying what it costs: moves are capped at max_change_percentage (20% by default) because Meta re-enters learning on large jumps. Returns the plan with before and after budgets, the reason per move, and the ad sets deliberately left alone. If every ad set performs close to the average, the honest plan is to change nothing.