fix(_dev,start): hide _dev and start commands from help output

[danielroe]

🔗 Linked issue

📚 Description

this is confusing for users

[coderabbitai]

📝 Walkthrough

Walkthrough

The internal _dev Nuxt CLI command is marked hidden, excluding it from help output and completions while keeping it runnable. End-to-end tests verify dispatch through both CLI entry points, and unit snapshots confirm _dev is absent from top-level usage and command listings.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
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.
Title check	✅ Passed	The title matches the main change of hiding the internal _dev command from help output, though it also mentions start which is not in this patch.
Description check	✅ Passed	The description is brief but still related to the goal of reducing user confusion by hiding an internal command.

✨ 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 fix/_dev

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[codspeed-hq]

Merging this PR will not alter performance

✅ 2 untouched benchmarks

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_{Comparing fix/_dev (21c3388) with main (a94b9f5)}

[pkg-pr-new]

• nuxt-cli-playground

  npm i https://pkg.pr.new/create-nuxt@1389
  

  npm i https://pkg.pr.new/nuxi@1389
  

  npm i https://pkg.pr.new/@nuxt/cli@1389
  

commit: 21c3388