Core 0.12.5 — reviewed authoring operations

Adds shared project authoring, draft contract scaffolding, source field mapping, and provider execution settings used by CLI and the VS Code companion. Node 22/24 CI, package validation, audit, and a fresh anonymous npm install passed. Published npm package: @ingestron/core@0.12.5 (sha512-xFLbFs6Qe3sJ+PTJ02AfgJhMu7o6CIry9T/x+8Rs0Iwt/EbCVkEhh649IZp5hs5E2lLcnWDTZXO34bDTemKibA==).