- Create SocialDraftPreview with platform icon, color, content, char count, media URLs, schedule display
- Integrate SocialDraftPreview into ApprovalInspector for social_post approvals
- Add schedule picker with immediate/scheduled radio group and datetime-local input
- Add social_post to type badge with accent styling
- Approve button shows 'Approve & Post' for social_post approvals
- Accessibility: role=region, aria-label, aria-live=polite, role=radiogroup
- Fix test type annotation for TS compatibility