ci: use staged npm publishing

[JoviDeCroock]

Summary

• Switches the trusted npm publish path to pnpm stage publish.
• Uses pnpm 11.3.0 and npm 11.15.0 in the publish workflow.
• Preserves Changesets tag/GitHub release creation by emitting package tags from the staging helper.
• Keeps the existing JSR publish step after npm packages are staged.

Verification

• node --check .github/scripts/stage-packages.mjs
• Workflow YAML parsed locally.

[cloudflare-workers-and-pages]

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[changeset-bot]

⚠️ No Changeset found

Latest commit: b640c5f

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.

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