Classify the Budget's new helper variables in the fiscal partition #2762

policyengine_uk/data/fiscal_partition.yaml gives every tax and spending variable an owner, so a measurement can tell a head from a component or an assessment. Eight helpers that recent changes added have no entry on main (2da212a):

• miscellaneous_income_trading_allowance_deduction
• uses_trading_allowance
• miscellaneous_income_before_trading_allowance
• income_not_otherwise_charged
• machine_games_standard_rate_higher_stake_net_takings
• carers_allowance_weekly_earnings_above_limit
• ebr_alternative_fuel_payment
• monthly_ebr_alternative_fuel_payment

The first five belong to tax heads. The other three belong to spending heads, and the file has no section for a component of a spending head.

Two related gaps sit nearby:

• No test covers the trading allowance's 2027 increase on income from both trade and Chapter 8 miscellaneous sources, which share one allowance since No Council Tax Rebate in Northern Ireland; add its £200 Alternative Fuel Payment #2735.
• No test checks Step 6 of the income tax calculation with the Pension Tax Allowance and finance cost relief applying together, including where tax runs out.

The fix should list the eight helpers, add a spending_exclusions section for the last three, and add those tests. It changes no calculated amount.