ci: add GitHub workflow for publishing dev releases

[christian-bromann]

This PR adds a new GitHub Actions workflow that enables maintainers to publish dev releases of individual packages for testing purposes.

What's New

Dev Release Workflow (.github/workflows/dev-release.yml)

A manually-triggered workflow that allows publishing pre-release versions of any package in the monorepo.

Features:

• 📦 Package Selection - Choose from all available packages (langchain, @langchain/core, @langchain/openai, etc.)
• 🌿 Branch Selection - Publish from any branch, not just main
• 🏷️ Customizable NPM Tag - Defaults to dev, but can be changed (e.g., beta, next, canary)
• 🔖 Version with Git SHA - Versions include the commit SHA for traceability (e.g., 1.1.0-dev.abc1234)

[changeset-bot]

⚠️ No Changeset found

Latest commit: 1455188

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[hntrl]

Do we just want to depend on prerelease modes?

https://github.com/changesets/changesets/blob/main/docs/prereleases.md

[christian-bromann]

@hntrl good call, switched to changesets, it now just publishes all packages that have changes. Also added a step to comment on any opened PR with given branch notifying that a dev release was published.