Pin Node runtime for pnpm installs

[ErisDS]

Summary

• Adds a root engines.node range matching Ghost core (^22.13.1) so tooling that reads the workspace root can detect that this repo is Node 22-only.
• Keeps the change intentionally narrow: no pnpm devEngines.runtime pin and no lockfile metadata changes.
• This is intended to help dependency artifact generation, including Renovate lockfile updates, align with Ghost's Node 22 runtime instead of falling back to Node 24.

Testing

• [ -s "$HOME/.nvm/nvm.sh" ] && . "$HOME/.nvm/nvm.sh" && nvm use 22.18.0 >/dev/null && pnpm install --frozen-lockfile --ignore-scripts

[coderabbitai]

Walkthrough

This PR adds a top-level engines object to package.json with "node": "^22.13.1". No other changes are present in the diff.

Suggested reviewers

• EvanHahn

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: pinning the Node runtime for pnpm installs via the engines field in package.json.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	The pull request description clearly explains the purpose of adding the engines.node constraint and how it aligns with Ghost's Node 22 runtime requirements.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch pin-node-runtime

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_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.81%. Comparing base (fcad5b8) to head (2608807).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #28064   +/-   ##
=======================================
  Coverage   73.81%   73.81%           
=======================================
  Files        1528     1528           
  Lines      129417   129417           
  Branches    15506    15506           
=======================================
  Hits        95527    95527           
- Misses      32910    32934   +24     
+ Partials      980      956   -24     

Flag	Coverage Δ
admin-tests	54.03% <ø> (ø)
e2e-tests	73.81% <ø> (ø)

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