Add Unraid mdstat support for MDADM detection

[Starosdev]

Summary

Add Unraid /proc/mdstat parsing support to the MDADM collector so Unraid-backed arrays can be detected and surfaced in Scrutiny.

Problem

Issue #530 is now validated on a standard Linux MDADM host, but Zeus still cannot populate MDADM arrays because Unraid does not expose the standard Linux mdadm /proc/mdstat format that the current detector expects.

Current detector expectation:

• lines like md0 : active raid1 ...

Observed live Zeus /host/proc/mdstat shape:

• key/value lines like mdState=STARTED
• diskNumber.0=...
• rdevName.0=sdd
• diskName.1=md1p1

So the current collector deployment on Zeus is healthy, but the detector logs:

• No MDADM arrays found in /proc/mdstat

That means Unraid remains unsupported for actual MDADM ingestion even when the container is wired correctly.

Evidence

Live Zeus testing on develop revision eb050029d65ff47c8eb24ecd09618f72471e13b4 showed:

• GET /api/health healthy
• authenticated GET /api/mdadm/summary returned {"data":[],"success":true}
• scrutiny-collector-mdadm run --debug logged:
  • Starting MDADM array collection
  • No MDADM arrays found in /proc/mdstat
  • No MDADM arrays found
• /host/proc/mdstat was mounted correctly, but contained Unraid key/value metadata instead of standard Linux mdX : active ... lines.

Separate validation on Helios confirmed that #530 itself is fixed on a standard Linux MDADM host:

• temporary loopback RAID1 array detected correctly
• repeated collector runs registered and updated the same array successfully
• no SQL logic error: row value misused (1) on re-registration

So this follow-up is about Unraid detection support, not the #530 registration bug.

Proposed Scope

• extend MDADM detection to recognize Unraid /proc/mdstat format
• map Unraid array metadata into the existing MDADMArray and MDADMMetrics structures where possible
• preserve current standard Linux MDADM parsing behavior
• add tests for both standard Linux and Unraid /proc/mdstat parsing
• verify on Zeus testing after implementation

Acceptance Criteria

• collector detects Unraid-backed arrays from Zeus-style /proc/mdstat
• Zeus scrutiny-dev can populate authenticated GET /api/mdadm/summary with real array entries
• standard Linux MDADM detection still works
• tests cover both parsing modes

Notes

This should stay scoped to detection/parsing support for Unraid's mdstat format. It should not reopen the backend registration work already addressed in #530.