Migrate release flow to release-please

[robert-northmind]

Context

The current release process documented in CONTRIBUTING.md uses yarn bump:version (= lerna version), which:

1. Bumps versions in all package.json files.
2. Commits, tags, and pushes directly to main in one shot.
3. The tag push triggers .github/workflows/release.yml → lerna publish from-package to npm.

This worked for v1.0.0 (2026-04-15) but an org-level ruleset added 2026-04-27 ("Public repo required PRs") now blocks direct pushes to main. Every change must go through a PR with at least one review approval. Tag pushes are not blocked, but the version-bump commit can no longer be pushed to main directly.

For v1.1.0 we are using a manual workaround: branch + lerna version --no-git-tag-version + PR + merge + tag main HEAD locally + push tag. This works but is error-prone and adds friction.

Proposal

Migrate to release-please:

• Conventional commits (which we already follow per CONTRIBUTING.md) drive the version bump.
• A bot maintains an automated "chore(release): X.Y.Z" PR with version bumps and CHANGELOG entries.
• Merging that PR creates the tag and triggers npm publish.
• No direct pushes to main — fully compatible with the ruleset.

This aligns with the faro-web-sdk sibling project, which is also migrating to release-please.

Acceptance criteria

• Add release-please-config.json and .release-please-manifest.json configured for the monorepo packages (packages/react-native, packages/react-native-tracing).
• Add a release-please GitHub Actions workflow that maintains the release PR.
• Verify release.yml (npm publish on tag push) still works with release-please-created tags. Adjust if needed.
• Update the "Release Process" section in CONTRIBUTING.md.
• Remove or deprecate the bump:version script in the root package.json.
• Smoke-test with a patch release.

References

• release-please docs: https://github.com/googleapis/release-please
• Sibling project: https://github.com/grafana/faro-web-sdk