Add Vitest testing framework with initial test suites

[Copilot]

The project had no test infrastructure despite significant JavaScript logic. This adds Vitest as the testing framework with 32 initial tests covering the most testable modules, plus a CI workflow.

Changes

• Vitest setup: vitest.config.js with globals enabled, node environment, .test.mjs pattern (ESM tests in a CommonJS project)
• Test scripts: npm test (single run) and npm run test:watch (dev mode) in package.json
• CI workflow: .github/workflows/tests.yml — runs on PRs and pushes to main
• Testability: Conditional module.exports in src/assets/js/games/config.js (no-op in browser via typeof module !== "undefined" guard)

Test coverage

Suite	Tests	Covers
tests/config.test.mjs	14	skillRarity() determinism, RARITY_WEIGHTS ordering, RARITY_COLORS format, GENERIC_SKILLS uniqueness
tests/eleventy-config.test.mjs	13	Directory config, currentYear shortcode, YAML extension compile/getData, randomPeople collection shuffle + immutability
tests/build-data.test.mjs	5	Export shape, repo URL, timestamp/hash presence

Conditional export pattern for browser JS

// At bottom of browser-side JS files
if (typeof module !== "undefined" && module.exports) {
  module.exports = { skillRarity, RARITY_WEIGHTS, /* ... */ };
}

[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	vitest@​4.1.2

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[socket-security]

Warning

Review the following alerts detected in dependencies.

According to your organization's Security Policy, it is recommended to resolve "Warn" alerts. Learn more about Socket for GitHub.

Action	Severity	Alert  (click "▶" to expand/collapse)
Warn		Obfuscated code: npm vite is 91.0% likely obfuscated Confidence: 0.91 Location: Package overview From: package-lock.json → npm/vitest@4.1.2 → npm/vite@8.0.3 ℹ Read more on: This package | This alert | What is obfuscated code? Next steps: Take a moment to review the security alert above. Review the linked package source code to understand the potential risk. Ensure the package is not malicious before proceeding. If you're unsure how to proceed, reach out to your security team or ask the Socket team for help at support@socket.dev. Suggestion: Packages should not obfuscate their code. Consider not using packages with obfuscated code. Mark the package as acceptable risk. To ignore this alert only in this pull request, reply with the comment @SocketSecurity ignore npm/vite@8.0.3. You can also ignore all packages with @SocketSecurity ignore-all. To ignore an alert for all future pull requests, use Socket's Dashboard to change the triage state of this alert.

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