Basement cleanup + rack layout for the first nodes

Parent epic: #1083 (basement cluster program). Project home: planning/roadmaps/basement-cluster.md.

Clear and lay out the server-room space for the first 3-5 machines per the epic 1 node selection: rack/shelf positions, cable paths, airflow, and where the boxed HDDs and spare machines stage. Layout sketch committed before anything moves.

Acceptance: layout committed; space for the first nodes clear and photographed.

Physical work notes

• Location: basement / server room, Osseo WI.
• Tools/parts: as listed in the task; note anything missing on this issue before starting.
• Safety: machines unplugged before drive or cable work; circuits are electrician-only work (epic 3).
• Verification: attach a photo of the finished state (and SMART/KVM output where relevant) to this issue before closing.