feat(ci): support branch-based prerelease without managing beta branch

[abueide]

Summary

Replace the beta branch force-push workflow with branch-based prereleases. Any feature branch can now publish prerelease versions without managing or syncing a secondary branch.

Key changes:

• Remove beta branch force-push step from release workflow
• Use current branch name for GITHUB_REF instead of hardcoded beta
• Configure semantic-release to treat any non-master branch as prerelease
• Update documentation with new fix candidate workflow

Benefits

• ✅ No branch management or syncing required
• ✅ Clear traceability: branch name appears in version (e.g., 2.23.0-fix-retry-bug.1)
• ✅ Multiple fix candidates can exist simultaneously on npm
• ✅ Each feature branch gets its own npm dist-tag
• ✅ Simpler mental model: branch = prerelease, master = stable

How it works

Publishing a fix candidate:

1. Push your feature branch (e.g., fix/customer-issue-123)
2. Go to Actions → Release workflow → Run workflow
3. Select your feature branch from dropdown
4. Choose beta as release type
5. Workflow publishes with branch name in version: 2.23.0-fix-customer-issue-123.1

Customer installation:

# Install latest from that branch's dist-tag
npm install @segment/analytics-react-native@fix-customer-issue-123

# Or pin to specific version
npm install @segment/analytics-react-native@2.23.0-fix-customer-issue-123.1

Test plan

• Run dry-run release from feature branch to verify version format
• Run beta release from feature branch and verify npm publish
• Verify customer can install using branch dist-tag
• Confirm multiple feature branches can have simultaneous prereleases

🤖 Generated with Claude Code