Add terminal position toggle and allow thinner review panel

[marcodenic]

• Add terminal position state (bottom/right) to layout context
• Extract TerminalPanel into reusable component with position toggle button
• Conditionally render terminal at bottom (full width) or right (stacked with review)
• Increase session panel max width from 45% to 75% to allow thinner review panel
• Show right panel when terminal is in right position even without review tabs
• Terminal takes full height when no review tabs are present
• Add dynamic padding to chat content to account for terminal height
• Add keyboard shortcut (ctrl+shift+) for terminal position toggle