feat(release): add manual prerelease workflow

[bao-cn]

Summary

Add a manual GitHub Actions workflow for publishing Terminal Blog prereleases from version branches.

Motivation

Releases need to be reproducible, branch-controlled, and reviewable. The repository currently documents release branches but has no supported path for building artifacts and creating a GitHub prerelease.

Implementation

• Add a workflow_dispatch-only Release workflow.
• Require the selected branch to match release/.
• Require a prerelease SemVer value and a dated CHANGELOG section.
• Run Prettier, ESLint, TypeScript, Vitest, and the production build.
• Package a source ZIP and Linux x64 standalone archive with SHA-256 checksums.
• Preserve the version Changelog and append GitHub-generated PR and contributor notes.
• Accept optional related Issue numbers during manual dispatch.
• Document the release workflow in README and CONTRIBUTING.

Behavior and compatibility

No application runtime or API behavior changes. The new workflow requires contents: write only for creating the release and tag.

Risk

Release creation is restricted to matching release/* branches, refuses existing tags, and always creates a prerelease. Failed runs cannot overwrite a published version tag.

Verification

• npx prettier --check .
• npm run lint
• npx tsc --noEmit --incremental false
• npm test (11 files, 32 tests passed)
• npm run build
• Parsed .github/workflows/release.yml with js-yaml.
• Added four release-note unit tests.

Screenshots or recordings

Not applicable; this pull request changes release automation and documentation.

Checklist

• I read and followed CONTRIBUTING.md.
• The change is focused and contains no unrelated dependency or generated-file churn.
• I added tests for Changelog extraction and release-note composition.
• I ran Prettier, ESLint, TypeScript, Vitest, and the production build locally.
• I updated README, CONTRIBUTING, and CHANGELOG.
• This Pull Request contains no secrets, environment files, or production data.