chore: publish typescript fixture to GitHub Packages

[jimisola]

Context

Part of the native-package axis of the parameterized regression test matrix. Once reqstool-client gains NpmLocation (reqstool-client PR #372), publish the TypeScript npm package to the GitHub Packages registry of reqstool/reqstool-regression so reqstool-client's NpmLocation can consume it.

Proposed approach

• Configure fixtures/ecosystems/typescript/package.json to publish a scoped npm package to GH Packages of reqstool/reqstool-regression
• Add a publish workflow to .github/workflows/ that calls the reusable typescript-publish-to-npm.yml with working-directory: fixtures/ecosystems/typescript
• Publish target: GitHub Packages of reqstool/reqstool-regression only (never the public npm registry — these are test fixtures)

Acceptance criteria

• fixtures/ecosystems/typescript/package.json configured to publish to GH Packages of reqstool/reqstool-regression
• Publish workflow wired up
• Artifact consumable via reqstool-client NpmLocation

Dependencies

• Depends on: feat(workflows): add working-directory input to reusable build/publish workflows .github#35 (reusable workflow needs working-directory input)
• Depends on: reqstool-client PR #372 (NpmLocation must exist to consume the artifact)

Moved from reqstool-client#389.