Revise income taxes related to retired military members

This bill revises Montana's income tax rules to better align state taxation with federal tax treatment for military pensions, retirement benefits, and survivor benefits. It expands the exemption for certain individuals who became Montana residents or remained residents after a specific date, removes a previous five-year limit on claiming this exemption, and eliminates a statutory sunset provision that would have ended the exemption. The legislation also amends existing tax code sections to clarify how various military-related income items are calculated for state tax purposes, ensuring consistency with federal tax definitions. These changes directly affect Montana residents receiving military retirement income and their dependents, providing more permanent tax relief without changing the fundamental structure of the state income tax system.