Consumer-facing documentation for the compute service

[scotwells]

Parent Issue

Tracked by datum-cloud/enhancements#682 (Launch Workload Compute Service — "UFOs")

Summary

There is currently no consumer-facing documentation for the compute service. Before launch, developers need enough documentation to successfully deploy their first workload without requiring hand-holding from the team.

Goals

• Publish a getting started / quickstart guide covering the end-to-end path from image to running instance
• Document how to build Unikraft-compatible images, including the differences from standard OCI containers that developers will encounter
• Publish API reference documentation for the compute.datumapis.com resource types (Workload, WorkloadDeployment, Instance)
• Document datumctl commands for compute resources once implemented
• Provide at least one reference workload / sample application demonstrating a realistic use case

Non-Goals

• Internal operator runbooks (tracked separately)
• Documentation for features not yet implemented

Open Questions

• Where does compute documentation live — docs.datum.net, GitHub, or both?
• Do we publish documentation before GA or only at GA?