Migrate from yarn to npm

[Copilot]

The repository used yarn as its package manager. This replaces yarn with npm across all tooling and CI.

Changes

• Lock file: Removed yarn.lock, generated package-lock.json via npm install
• package.json: Added "lint": "eslint src" script
• .github/workflows/pr-pipeline.yml: Replaced yarn commands with npm equivalents
• build/pipeline.yml / build/pre-release.yml: Replaced yarn commands with npm equivalents

Command mapping

Before	After
yarn install --frozen-lockfile	npm ci
yarn run <script>	npm run <script>
yarn eslint src	npm run lint

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[rzhao271]

@copilot Check that eslint is a devdependency now and regenerate the lock file

[Copilot]

@copilot Check that eslint is a devdependency now and regenerate the lock file

eslint is indeed a devDependency in package.json (along with @typescript-eslint/eslint-plugin, @typescript-eslint/parser, eslint-plugin-header, etc.). The package-lock.json was generated via npm install in commit f38afad and is already up to date — re-running npm install produces no changes to the lock file.

[rzhao271]

@copilot Resolve merge conflict

[Copilot]

@copilot Resolve merge conflict

Done in 85fd52e. Merged origin/main (ESLint 9 flat config, #798) into this branch. The only conflict was yarn.lock — kept it deleted. Also removed package-lock.json from .gitignore (main had added it, but we want to track it), and regenerated package-lock.json with the updated ESLint 9 dependencies.

[rzhao271]

@copilot Do not use npx. Add new lint script.

[Copilot]

@copilot Do not use npx. Add new lint script.

Done in eae4b38. Added "lint": "eslint src" to package.json scripts and updated all CI files to use npm run lint instead of npx eslint src.