Implements comprehensive mdadm RAID array monitoring for Linux hosts
via pulse-host-agent. Arrays are automatically detected and monitored
with real-time status updates, rebuild progress tracking, and automatic
alerting for degraded or failed arrays.
Key changes:
**Backend:**
- Add mdadm package for parsing mdadm --detail output
- Extend host agent report structure with RAID array data
- Integrate mdadm collection into host agent (Linux-only, best-effort)
- Add RAID array processing in monitoring system
- Implement automatic alerting:
- Critical alerts for degraded arrays or arrays with failed devices
- Warning alerts for rebuilding/resyncing arrays with progress tracking
- Auto-clear alerts when arrays return to healthy state
**Frontend:**
- Add TypeScript types for RAID arrays and devices
- Display RAID arrays in host details drawer with:
- Array status (clean/degraded/recovering) with color-coded indicators
- Device counts (active/total/failed/spare)
- Rebuild progress percentage and speed when applicable
- Green for healthy, amber for rebuilding, red for degraded
**Documentation:**
- Document mdadm monitoring feature in HOST_AGENT.md
- Explain requirements (Linux, mdadm installed, root access)
- Clarify scope (software RAID only, hardware RAID not supported)
**Testing:**
- Add comprehensive tests for mdadm output parsing
- Test parsing of healthy, degraded, and rebuilding arrays
- Verify proper extraction of device states and rebuild progress
All builds pass successfully. RAID monitoring is automatic and best-effort
- if mdadm is not installed or no arrays exist, host agent continues
reporting other metrics normally.
Related to #676
