Description

When a panel is focused, pressing z should expand it to fill the full content area temporarily. This is especially useful for News, Calendar, Sports, and Feeds panels which are cramped at normal size.

Implementation:

• Bind z when a panel has focus (or as an app-level binding that acts on the focused panel)
• Push a ModalScreen or use CSS to show only the focused panel at full size
• Zoomed panel still polls/updates normally
• Esc or z again collapses back to the normal layout
• Zoomed state is displayed with a "[zoomed — Esc to close]" hint in the border title

Depends on: TASK-005 (tab focus cycling)

Acceptance Criteria

• #1 z on a focused panel expands it full-screen
• #2 Esc collapses back to normal layout
• #3 Data continues to update in zoomed state
• #4 Zoom hint visible in border title
• #5 Works on all 3 pages