分舟载模，共引一源 · Split runtime from the Small model facade

[eric8810]

Summary

• accept D107 for the N2 runtime/model/meta topology
• add npm workspaces under packages/* without treating the CMake native tree as a package
• add a private model-free @arcships/light-ocr-runtime that requires bundlePath
• add a private Small facade that preserves the current API, shared OcrError, and light-ocr bin
• keep bindings/node as the unchanged 0.3.x release source until cutover
• add one lightweight workspace contract step to the existing PR job

Verification

• npm run typecheck
• npm run test:workspace (5/5)
• dry-run packed both workspaces; each tarball contains only its intended source and legal files
• workspace light-ocr info --version returned npm/core 0.3.4 and the current native model
• workspace CLI recognized the generated banner through a full-page ROI

Scope

This starts N2 stage 1 only. It does not publish runtime, tiny, medium, or a 0.4.0 facade.