Add Asset Store packaging, store workflow, and version bumping

- packaging/asset-store/export-unitypackage.sh: builds
  .unitypackage without Unity Editor (gzipped tar with GUIDs)
- packaging/asset-store/asset-store-metadata.json: submission
  template for Unity Asset Store
- store-publish.yml: build .unitypackage on v* tags, attach to
  GitHub Release, optional Asset Store submission
- scripts/bump-version.sh: single entry point for releasing,
  updates package.json, commits and tags

All publishing is tag-driven: bump-version.sh → git push --tags
→ release.yml (UPM) + store-publish.yml (Asset Store)

Co-Authored-By: claude-flow <ruv@ruv.net>

add documentation

prepare for publication