Add timestamps to specialist status reports

Problem

When specialists (review-agent, test-agent) report status like \"Test Analysis Complete\" or \"Review Passed\", there's no timestamp visible to indicate when this happened. This makes it difficult to know if a status report is from a recent run or a stale cached result.

Current Behavior

• Agent says \"Ready for final review\" but dashboard shows old test status
• No way to tell if \"testStatus: failed\" is from 5 minutes ago or 5 hours ago
• updatedAt field exists in review-status.json but isn't prominently displayed

Proposed Solution

1. Add visible timestamps in dashboard for review/test status updates
2. Add timestamps to agent output when reporting completion:

• \"[2026-02-04 01:45:32] Test Analysis Complete ✅\"
• \"[2026-02-04 01:46:15] Review Passed - queuing test-agent\"

1. Show relative time in UI: \"Tests failed 15 minutes ago\"
2. Highlight stale status - if status is >30 min old, show warning

Acceptance Criteria

• [ ] Dashboard shows timestamp for last review status update
• [ ] Dashboard shows timestamp for last test status update
• [ ] Specialists include timestamps in their completion messages
• [ ] Stale status (>30 min) is visually indicated
• [ ] Status history is preserved (last N status changes with timestamps)

Priority

High - Essential for understanding agent workflow state