Pin npm to 11.x to fix release publish (sigstore bundling bug)

[nolannbiron]

Problem

The Release job fails at changeset publish with npm error Cannot find module 'sigstore' (from libnpmpublish/lib/provenance.js).

npm 12.0.0 (released 2026-07-08) ships without the bundled sigstore module that libnpmpublish requires to generate provenance. The workflow ran npm install -g npm@latest, picking up the broken 12.0.0, so publishing with NPM_CONFIG_PROVENANCE: true crashes. Upstream: npm/cli#9722.

The crash happens before any package is pushed, so @gitbook/api@0.187.0 (bumped by #1236) never reached npm.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 71b7d27

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

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[pkg-pr-new]

Open in StackBlitz

bun add https://pkg.pr.new/GitbookIO/integrations/@gitbook/api@1237

commit: 71b7d27