[STG-2001] feat: migrate OpenClaw Browserbase package

[shrey150]

Summary

• Migrates @browserbasehq/openclaw-browserbase into packages/openclaw-browserbase
• Adds packages/* to the pnpm workspace and root Changesets release scripts/config
• Adds a root release workflow for Changesets release PRs and npm publishing with GitHub OIDC
• Adds a patch changeset so the first release from this repo bumps from the already-published 0.1.0

Linear: https://linear.app/browserbase/issue/STG-2001/migrate-openclaw-browserbase-package-into-integrations

Release CI / npm publishing

This PR preserves the publishing path in-repo, but npm Trusted Publishing needs to be moved from browserbase/openclaw-browserbase to this repo before the publish job can succeed:

1. In npm, configure @browserbasehq/openclaw-browserbase Trusted Publisher to use repository browserbase/integrations.
2. Set the workflow filename field to release.yml (the file lives at .github/workflows/release.yml).
3. Leave environment unset unless npm currently requires one for this package.

Without that npm-side Trusted Publisher update, changeset publish should be able to create release PRs but the actual npm publish step is expected to fail authorization.

Validation

• pnpm install --no-frozen-lockfile
• pnpm run build:packages
• pnpm exec eslint packages/openclaw-browserbase (passes with existing any warnings from the OpenClaw plugin API surface)
• npm pack --dry-run in packages/openclaw-browserbase
• pnpm exec changeset status --verbose shows @browserbasehq/openclaw-browserbase -> 0.1.1

Note: root pnpm run lint currently fails before reaching this package because examples/integrations/vercel/vercel-puppeteer/eslint.config.mjs imports @eslint/eslintrc, which is not a root dependency.