Add release workflow with bundle validation

[lukewilliamboswell]

Summary:

• add a dispatch-based release workflow that builds the package bundle, uploads it as an artifact, tests the downloaded bundle on Linux/macOS/Windows, and creates a GitHub release with the bundle asset
• add reusable bundle and bundle-example test helpers
• remove the old release-published bundle uploader to avoid duplicate bundle uploads, and move docs generation to nightly-new-compiler

Tests:

• python3 -m py_compile ci/test_bundle_examples.py
• bash -n scripts/bundle.sh
• ruby -e 'require "yaml"; ARGV.each { |file| YAML.load_file(file); puts file }' .github/workflows/release.yml .github/workflows/generate-docs.yaml .github/workflows/tests.yaml
• ROC=roc ./ci/all_tests.sh
• scripts/bundle.sh --output-dir dist
• python3 ci/test_bundle_examples.py --bundle-path dist/7Y6RP8ZkiMq8Vm7qQLGzm8cyEvww5EVT3YekRASH5VBg.tar.zst