Improve mobile layout for category chips and filter row

[akuligowski9]

On small screens the category chips row and column toggle can feel cramped. There's room to improve the mobile experience here.

Issues to address

• Category chips row and column toggle compete for horizontal space on narrow screens
• Active filters aren't always obvious on mobile
• Touch targets could be larger

Acceptance criteria

• Clean layout on screens 375px and up
• Column toggle accessible without scrolling
• No horizontal overflow