chore(ci): add matrix workflow to build demo apps [skip i18n]

[L16-code]

chore(ci): add matrix workflow to build demo apps [skip i18n]

This PR introduces a GitHub Actions workflow that builds each demo app in isolation using a matrix:

• demo/next-app
• demo/vite-project
• demo/adonisjs
• demo/react-router-app

Key improvements:

• Consistent Node (20.12.2) and pnpm (9.12.3) setup
• pnpm store and Turbo cache for faster CI runs
• Turbo filtered builds per demo to catch regressions early
• Build logs uploaded as artifacts on failure for easier debugging

Context and rationale: Fixes #1355

[amankamlesh]

@krsunny99 can you send link of your github action showing workspace running fine

[Copilot]

Pull Request Overview

This PR adds a new GitHub Actions workflow to build demo applications in isolation using a matrix strategy, improving the CI pipeline's ability to catch regressions early in individual demo apps.

• Implements matrix builds for 4 demo apps (next-app, vite-project, adonisjs, react-router-app)
• Adds pnpm store and Turbo caching to optimize build performance
• Captures build logs as artifacts on failure for easier debugging

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[Copilot]

The actions/cache@v3 action is outdated. Since actions/upload-artifact@v4 is being used elsewhere in this workflow (line 66), it would be more consistent to use actions/cache@v4 here as well. Using the latest version provides better performance and compatibility with current GitHub Actions infrastructure.

Suggested change

	uses: actions/cache@v3
	uses: actions/cache@v4

[Copilot]

The --force flag forces Turbo to rebuild without using cache, which defeats the purpose of setting up Turbo caching in line 54-55. This will significantly slow down CI runs. Consider removing the --force flag to allow Turbo to use its cache for faster builds, or document why cache invalidation is necessary for these builds.

Suggested change

	pnpm turbo build --force --filter ./demo/${{ matrix.app }} 2>&1 | tee logs/build-${{ matrix.app }}.log
	pnpm turbo build --filter ./demo/${{ matrix.app }} 2>&1 | tee logs/build-${{ matrix.app }}.log