Add release-saga.sh for E2E release automation

Full pipeline script that:
- Checks/installs gh CLI
- Runs local cargo tests
- Creates and pushes git tag
- Monitors GitHub Actions release workflow
- Verifies release artifacts
- Reports success with download links

Usage: ./scripts/release-saga.sh 0.1.0

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: crisdosaygo