chore: update release workflow by updating npm and adjusting node setup

[olliethedev]

Note

Low Risk
Changes are confined to the GitHub Actions release workflow; main risk is a release/publish failure if npm/pnpm assumptions differ in CI.

Overview
Modernizes the release GitHub Actions workflow by consolidating Node setup (including npm registry config) and adding a step to update npm to the latest version before installing dependencies.

Switches the publish step from pnpm publish (with --no-git-checks/token env) to npm publish while preserving provenance and the computed npm dist-tag gating (pre-release tags vs latest only from main).

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