Give operators a way to read and query inventory from datumctl #204

Downstream client work for milo-os/inventory#34 — M6: Audit & query, under the physical-inventory enhancement datum-cloud/tmp_datum-cloud_enhancements_713_Physical-inventory-f_2138d0c1#1.

Context

The inventory operator (inventory.miloapis.com/v1alpha1) ships cluster-scoped CRDs — Region, Site, Cluster, Node, NetworkDevice, Link, Provider, Rack, Port, Cable, Circuit, VirtualMachine — on the Milo control plane. M6 makes them auditable (Activity capability) and queryable (printer columns, topology.* labels, field indexers). datumctl is the first operator-facing client.

Audience is staff / operators, not per-project consumers.

Goal

Confirm operators can discover, read, and audit inventory through datumctl — mostly via the existing kubectl-style surface, plus activity query. New code only where gaps exist.

Tasks

• datumctl api-resources lists all inventory kinds against a control plane with the CRDs installed
• datumctl get <kind> / describe <kind> work and render the printer columns M6 defines (key refs, type, topology)
• --selector topology.inventory.miloapis.com/...=… returns assets by region/site/cluster/rack
• datumctl activity query --filter "<CEL>" returns readable inventory timelines (verify against the ActivityPolicies M6 ships) — e.g. filter objectRef.apiGroup == 'inventory.miloapis.com'
• Identify and file any gaps (missing convenience views, output formatting) as follow-ups; no new view code unless a gap blocks operators

Depends on

• M6 datum-cloud/datum-os#370 ActivityPolicies + printer-column pass merged and deployed to the target control plane.

Non-goals

• No project-scoped / consumer-facing inventory surfacing — operators only.

cc @scotwells