Extend US annual static aging to 2036 #1280

Part of the US 2036 extension, tracked in PolicyEngine/policyengine-api#3926. CBO's February 2026 baseline and its 2027–2036 budget window run through 2036, and the canonical SPM forecast now covers 2022–2036 (PolicyEngine/spm-calculator#51). This doesn't block the extension: the annual US projection candidates are used only once PolicyEngine/policyengine.py#524 activates annual US datasets.

@MaxGhenis, when that lands, raise the default end year from 2035 to 2036 in three places:

• packages/microcosm-build/src/microcosm/build/us_annual_static_aging.py: the end_year: int = 2035 default (line 209) and the --end-year CLI default (line 462);
• docs/us-annual-static-aging.md: "2035 by default" and the example command's --end-year 2035.

🤖 Generated with Claude Code