Propose a budget reallocation (writes nothing)

Produces a plan for moving budget between campaigns, based on what each one currently returns and whether it is actually budget-limited. It changes nothing. Applying any line of the plan means calling google_update_campaign_budget for that campaign, which the user approves separately. Use when: the user asks where their money should go and several campaigns have enough data to compare. Do not use when: campaigns have very different objectives (brand versus prospecting), or when a campaign has fewer than about 15 conversions in the window — the comparison is then noise dressed up as arithmetic. Say that instead of producing a plan. The heuristic: rank campaigns by cost per conversion (or by ROAS when you ask for value), raise the efficient ones that are spending their budget, lower the inefficient ones, cap every move at max_change_percentage, never go below min_daily_budget, and keep the account total the same unless you ask otherwise. Proposed budgets are whole multiples of the smallest amount Google bills in the account currency (a whole yen or won, a cent for most others), so any line can be applied exactly as shown. A campaign that is not spending its budget will not spend more just because the budget goes up: the plan says so rather than proposing a rise. If you are unsure which account, campaign or period the user means, ask them — do not guess ids or dates.