feat: add --extends option to support nuxt layer extension

[sanjayy-gowdaa]

🔗 Linked issue

Resolves #930

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

This PR adds a new --extends CLI option to core Nuxt commands, enabling users to extend Nuxt layers directly from the command line. This addresses the need for a unified CLI experience across the Nuxt ecosystem.

Problem: Currently, projects like Docus need to create their own CLI tools (e.g., docus build)

Changes:

• Add extendsArgs to _shared.ts for consistent argument definition
• Add --extends support to core commands: build, dev, generate, preview
• Add --extends support to utility commands: analyze, typecheck, prepare

[pkg-pr-new]

nuxt-cli-playground

npm i https://pkg.pr.new/create-nuxt@933

npm i https://pkg.pr.new/nuxi@933

npm i https://pkg.pr.new/@nuxt/cli@933

commit: 11a55a7

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 18.91892% with 30 lines in your changes missing coverage. Please review.

Please upload report for BASE (main@50b1fcf). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
packages/nuxi/src/commands/typecheck.ts	0.00%	5 Missing ⚠️
playground/some-layer/pages/extended.vue	0.00%	4 Missing and 1 partial ⚠️
packages/nuxi/src/commands/dev.ts	0.00%	4 Missing ⚠️
packages/nuxi/src/commands/analyze.ts	0.00%	3 Missing ⚠️
packages/nuxi/src/commands/build.ts	0.00%	3 Missing ⚠️
packages/nuxi/src/commands/prepare.ts	0.00%	3 Missing ⚠️
packages/nuxi/src/commands/preview.ts	0.00%	3 Missing ⚠️
packages/nuxi/src/commands/generate.ts	0.00%	2 Missing ⚠️
packages/nuxi/src/dev/utils.ts	0.00%	1 Missing ⚠️
playground/some-layer/nuxt.config.ts	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #933   +/-   ##
=======================================
  Coverage        ?   12.52%           
=======================================
  Files           ?       74           
  Lines           ?     3897           
  Branches        ?      112           
=======================================
  Hits            ?      488           
  Misses          ?     3375           
  Partials        ?       34           

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[codspeed-hq]

CodSpeed Performance Report

Merging #933 will not alter performance

_{Comparing sanjayy-gowdaa:extends-layer (11a55a7) with main (50b1fcf)}

Summary

✅ 2 untouched benchmarks

[danielroe]

this looks great - thank you ❤