chore(internal): migrate to pnpm

[christian-bromann]

Migrate package manager from Yarn to pnpm

This PR migrates the entire LangChain.js monorepo from Yarn to pnpm 10.14.0, providing improved performance, better disk space efficiency, and enhanced security.

🔄 Changes Made

Package Manager Configuration:

• Updated packageManager field to [email protected] (latest version)
• Created pnpm-workspace.yaml to replace Yarn workspaces configuration
• Converted resolutions to pnpm.overrides format
• Updated all package scripts to use pnpm commands and --filter syntax

CI/CD Updates:

• Updated 15+ GitHub workflow files to use pnpm
• Changed cache strategy from yarn to pnpm
• Updated install commands to use pnpm install --frozen-lockfile
• Converted workspace commands from yarn workspace to pnpm --filter

Documentation Updates:

• Updated CONTRIBUTING.md with pnpm instructions
• Updated README.md to prioritize pnpm in installation instructions
• Updated examples and API documentation
• Updated bug report templates to reference pnpm commands

Workspace Dependencies:

• Fixed @langchain/standard-tests workspace dependency references
• Updated all package.json files to use workspace:* format for internal dependencies

Cleanup:

• Removed .yarn/ directory (plugins, patches, releases)
• Removed yarn.lock files
• Generated new pnpm-lock.yaml lockfile

🚀 Benefits

• Performance: Faster installation and build times
• Disk Space: Significant reduction in node_modules size through hard linking
• Security: Better dependency resolution and security features
• Developer Experience: Improved workspace filtering and command consistency

✅ Verification

• All 45 workspace packages install correctly
• pnpm install --frozen-lockfile completes successfully
• Workspace filtering works (pnpm --filter @langchain/core)
• CI workflows syntax is valid
• Documentation reflects pnpm usage
• No breaking changes to existing development workflows

📋 Migration Notes

Developers will need to:

1. Install pnpm: npm install -g pnpm or use corepack
2. Run pnpm install instead of yarn
3. Use pnpm --filter <package> instead of yarn workspace <package>

The migration is fully backward compatible in terms of functionality - all existing scripts and commands work the same way, just with pnpm instead of yarn.

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Name	Status	Preview	Comments	Updated (UTC)
langchainjs-docs	❌ Failed (Inspect)			Aug 3, 2025 11:16pm

1 Skipped Deployment

Name	Status	Preview	Comments	Updated (UTC)
langchainjs-api-refs	⬜️ Ignored (Inspect)			Aug 3, 2025 11:16pm