## Why

The Headquarter web app is currently unusable on mobile devices. Critical workflows—starting and stopping sessions, viewing instance status, and making small configuration adjustments—are blocked by desktop-oriented layouts, missing touch targets, and broken responsive behavior. Since users perform real work through terminal sessions (already mobile-optimized) and session management, the core app shell and key pages must be at least functional on phones.

## What Changes

- **Mobile navigation**: Replace horizontal scroll nav with bottom tab bar on mobile breakpoints
- **Session management mobile layout**: Redesign session cards for touch, add swipe actions, ensure all controls are reachable
- **Dashboard mobile view**: Simplify summary cards, optimize quick actions for touch
- **Responsive forms**: Stack multi-column forms vertically on mobile, ensure touch targets ≥ 44px
- **Mobile-optimized dialogs**: Ensure all dialogs fit within 320px viewport, add scroll when needed
- **Page headers**: Add consistent back buttons and contextual action bars on mobile
- **Touch feedback**: Add active states and loading indicators for all interactive elements
- **Graceful degradation**: Complex admin pages (Tool Workshop, Config Profiles) get read-first mobile views with edit capability

## Capabilities

### New Capabilities
- `mobile-navigation`: Bottom tab bar, page transitions, and mobile-specific navigation patterns
- `mobile-session-management`: Touch-optimized session cards, swipe actions, and mobile session controls
- `mobile-responsive-layouts`: Breakpoint system, touch targets, and form stacking for mobile viewports

### Modified Capabilities
- `frontend-foundation`: Add mobile breakpoint system and responsive grid utilities
- `session-lifecycle-ux`: Extend session management UX with mobile-specific interactions
- `tool-instances`: Ensure instance controls (start/stop/restart) are usable on mobile

## Impact

- **Frontend**: Major CSS changes to AppShell, page layouts, form components, and card patterns
- **Components**: New MobileNav component, updates to SessionCard, CreateSessionForm, and all page components
- **User Experience**: Significantly improved mobile usability without reducing desktop functionality
- **No API changes**: Purely frontend/CSS work
