- PrdService owns create/read/update/link/import/export; wizard and package
CLI become prompt layers over the service (no second writer path)
- PRD documents gain a content version and a missions linkage array persisted
in the YAML authority store (survives restart); linkage writes do not bump
the content version
- exportMarkdown renders a labeled generated view (id + version + do-not-edit
header) that no code path reads back; the store loads .yaml/.yml only
- importDocument validates structure with zod before anything else, persists
valid imports as draft (validity is not approval), and refuses conflicts
with a typed PrdImportConflictError carrying a proposed successor; the
original document stays byte-identical until acceptSuccessor
- raw store writers (createPrd/savePrd) are no longer exported from the
package entry point
