[Enhancement] Migrate from npm to pnpm

[vincentkoc]

Description

Migrate package manager from npm to pnpm for better performance and consistency with MCP ecosystem.

Benefits

• Faster installations
• Better disk space efficiency
• Stricter dependency resolution
• Built-in monorepo support (future-proofing)
• Industry standard for MCP servers

Tasks

• Add pnpm-workspace.yaml (for future monorepo support)
• Convert package-lock.json to pnpm-lock.yaml
• Update all workflows to use pnpm
  • .github/workflows/ci.yml
  • .github/workflows/deploy.yml
  • Any other workflows
• Update README with pnpm commands
• Update CONTRIBUTING.md
• Add .npmrc with pnpm settings
• Test full installation flow
• Update documentation

Workflow Changes

Replace:

- run: npm ci
- run: npm test

With:

- uses: pnpm/action-setup@v2
  with:
    version: 8
- run: pnpm install --frozen-lockfile
- run: pnpm test

References

• All reference MCP implementations use pnpm
• Browserbase, Supabase, Everything servers use pnpm