- Track plain-text render mode per assistant message (including streaming output) in ChatView state
- Add inline mobile-only Eye/EyeOff toggle buttons on assistant bubbles to switch markdown vs plain text per message
- Hide the header markdown/plain toggle on mobile and polish inline toggle sizing, focus, and hover styles in ChatView.css
- Extend ChatView tests with mobile viewport coverage for toggle rendering, per-message isolation, round-trip toggling, and mobile CSS contract checks