chore: migrate publish workflows to PNPM

[daniel-graham-amplitude]

Summary

• Change the publish workflow scripts to use pnpm
• Changed the publish scripts from "lerna" to "pnpm" because "lerna" doesn't rename the "workspace:*" (bonus: PNPM will check if a package exists in NPM registry before publishing it, preventing the problem we had in the past with not being able to republish)

Checklist

• Does your PR title have the correct title format?
• Does your PR have a breaking change?: No

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Note

Moves release automation to pnpm and streamlines prerelease/release flows.

• Replace yarn/npm commands with pnpm across publish-single-package.yml and publish-v2.yml (setup pnpm, use pnpm for build/test/lint/version/publish)
• Change default releaseType to prerelease and add explicit dry-run steps: deploy:version:dry-run, deploy:publish:dry-run; add deploy:pack
• Update publish commands to use pnpm deploy:publish with --tag (beta or preid) and adjust single-package publish to pnpm publish
• Add pnpm caching in Actions and update version banner in src/version.ts
• Bump lint-staged and refresh pnpm-lock.yaml (transitive dependency updates)

^{Written by Cursor Bugbot for commit 8506aaf. This will update automatically on new commits. Configure here.}

[macroscopeapp]

Migrate publish workflows to pnpm for amplitude-typescript to meet NPM security remediations in .github/workflows/publish-single-package.yml and .github/workflows/publish-v2.yml

Switch CI versioning and publish steps to pnpm, default workflow_dispatch.releaseType to prerelease, and add dry-run scripts in package.json.

🖇️ Linked Issues

This pull request fulfills the migration in AMP-145286 under the NPM Security Remediations epic AMP-145285 and contributes to the initiative AMP-91393.

📍Where to Start

Start with the workflow changes in .github/workflows/publish-v2.yml, then review the corresponding pnpm scripts in package.json.

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Macroscope summarized 8506aaf.

[Mercy811]

LGTM!