Fast-forward an OpenSpec change

Generate every artifact the schema requires before implementation can start, without pausing between them, then hand off to implementation.

Steps

1. Ensure the project schema is installed. Check whether openspec/config.yaml and openspec/schemas/rhdh-spec-driven/ already exist. Only if either is missing, invoke /rhdh-spec-driven-schema and run its project-install step. Then confirm with openspec schemas --json.
2. Get the change name or description. Derive a kebab-case name from a description if no name was given (e.g. "add user authentication" -> add-user-auth); do not proceed without knowing what to build.
3. Create the change directory (skip if it already exists — see Guardrails): openspec new change "<name>" (default schema from openspec/config.yaml, or pass --schema rhdh-spec-driven).
4. Get the build order: