Release v0.8.4

[knowledgecode]

Summary

• Bump version to 0.8.4
• Update Vitest and related dependencies
• Update Vitest Playwright configuration

Changes

Dependencies Update

• Vitest: 3.2.4 → 4.0.3
• Vite: 7.1.9 → 7.1.12
• ESLint: 9.37.0 → 9.38.0
• typescript-eslint: 8.46.0 → 8.46.2
• Replace @vitest/browser with @vitest/browser-playwright

Configuration Updates

• Update vitest.config.ts to use playwright function from @vitest/browser-playwright
• Maintain Playwright installation step in CI workflow

Test Plan

• Verify build succeeds locally
• Verify tests pass locally
• Verify CI completes successfully
• Verify linter passes