Add changesets and npm publish workflows with OIDC trusted publishers

[clavery]

Summary

• Add Changesets for version management and changelog generation
• Create two-workflow architecture for npm publishing with OIDC trusted publishers
• Configure linked versioning for b2c-cli, b2c-tooling-sdk, and b2c-dx-mcp
• Add comprehensive documentation in PUBLISHING.md

Workflows

changesets.yml - Version Management

• Triggers on push to main
• Creates/updates "Version Packages" PR when changesets exist
• Does NOT publish (no id-token: write needed)

publish.yml - npm Publishing

• Triggers on git tag push (e.g., v1.0.0, v1.0.0-beta.1)
• Publishes to npm using OIDC trusted publishers
• Has id-token: write permission for npm trusted publishers
• Creates GitHub Release automatically

Release Workflow

Developer runs `pnpm changeset` → creates changeset file
          ↓
PR merged to main
          ↓
changesets.yml creates "Version Packages" PR
          ↓
"Version Packages" PR merged (updates versions + changelogs)
          ↓
Maintainer pushes tag: git tag v1.0.0 && git push origin v1.0.0
          ↓
publish.yml publishes to npm via OIDC

Files Changed

File	Description
.changeset/config.json	Changesets configuration
.changeset/README.md	Auto-generated changeset docs
.github/workflows/changesets.yml	Version management workflow
.github/workflows/publish.yml	npm publish workflow with OIDC
package.json	Added changeset scripts
README.md	Updated release section
PUBLISHING.md	Detailed publishing documentation

Post-Merge Setup Required

1. First-time publish - Manually publish initial versions to npm (packages must exist before configuring trusted publishers)
2. Configure trusted publishers on npmjs.com for each package:
   • Owner: SalesforceCommerceCloud
   • Repository: b2c-developer-tooling
   • Workflow: publish.yml

Test plan

• pnpm changeset status works
• pnpm run build succeeds
• Verify workflow syntax after merge (GitHub Actions tab)
• Test with dry-run: pnpm publish -r --access public --dry-run