Add specs/ProductRequirementsDocument.md: hybrid product PRD (sister-repo
skeleton plus the template's Formal Standards / Related Concepts /
Appendix sections), heavy FR/NFR with Requirement/Details/Acceptance
triplets, Canon Alignment, 12 functional + 8 non-functional requirements,
conceptual model, MVP, roadmap, risks, and orientation-map appendix.
Substance traces to INTENT, ArchitectureBlueprint, ecosystem-boundaries,
and the research digest; no scope invented beyond repo-boundary.
Fix relative links broken by the ArchitectureBlueprint.md move into
specs/ (its own INTENT/SCOPE/research links and the ecosystem-boundaries
back-reference).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
