add backend endpoint for publish readiness checks
enforce publish gate contract before version publication
make publish preconditions explicit and consistent for clients
add backend endpoints for pricing coverage analysis and unpriced seat inspection
add explain endpoint to make effective pricing decisions traceable
improve pricing diagnostics for admin and editor workflows
extend test seat preview with explicit sellability reason codes
serialize preview price amount as string for a stable API contract
improve diagnosis of non-sellable states for preview consumers
- add typed response schemas for pricing write endpoints
- add stale draft version guard for pricing mutations
- unify pricing API contract around expected_scheme_version_id
- update API route map
- add smoke regression checklist for backend routes and artifact flows
