Add availability_updated_at to list_members MCP output

## REVIEWER AUDIT - APPROVED ✓ ### Implementation Review **Scope**: Exactly 2 files modified - both directly related to ticket scope ✓ **Acceptance Criteria - All Met**: | Criteria | Status | Details | |----------|--------|---------| | Includes `availability_updated_at` | ✓ | Added to MCP output | | ISO 8601 format | ✓ | Uses `.iso8601` method | | Handles nil gracefully | ✓ | Safe navigation `&.` operator | | Test coverage | ✓ | New test verifies both fields | ### Code Quality **MCP Controller** (`app/controllers/api/v1/mcp_controller.rb:408-413`): ```ruby { name: m.name, role: m.agent_type, active: m.active?, availability_status: m.availability_status, # Bonus fix availability_updated_at: m.availability_updated_at&.iso8601, # Safe nil handling assigned_count: m.assigned_tickets.where(status: %w[in_progress pending_audit]).count } ``` - ✓ Safe navigation `&.` prevents errors if field is nil - ✓ ISO 8601 format via Rails `.iso8601` method - ✓ Bonus: Also added `availability_status` which was previously missing - ✓ Updated tool description to document all output fields ### Test Coverage New test verifies: 1. `availability_status` is included in output 2. `availability_updated_at` is included in output 3. ISO 8601 format validated with regex: `/\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}/` **Status**: PASS_AUDIT - Ready for human approval