At 860 px and under, opening the timelines table widened main's single grid column to the table's width: every card grew to ~815 px on a 420 px screen, and the redraws set off "ResizeObserver loop completed with undelivered notifications". Grid items now keep min-width 0, so a wide table scrolls inside its own frame.
At 420 px, toggling every table over all periods × breakdowns used to log 16 ResizeObserver warnings and widen the page to 1,563 px. It now logs none and stays at 405 px. 1280 px is unchanged.
Timelines table open, before → after, 420 dark, light; 1280 dark, light:
🤖 Generated with Claude Code