Add Vanilla JS + Yii3 co-work example (JSON API + fetch)

[Ai-TOS-789]

Summary

Adds a minimal, dependency-free example of Vanilla JS working together with a Yii3 backend, demonstrating the recommended way to:

• return JSON from an action (ResponseFactoryInterface)
• expose a JSON API route
• serve plain JS/CSS through AssetBundle (auto-published to public/assets)

Changes

• src/Web/Api/HealthAction.php (new): GET /api/health JSON endpoint.
• config/common/routes.php: register Route::get('/api/health').
• src/Web/Shared/Layout/Main/MainAsset.php: register app.js in $js.
• assets/main/app.js (new): Vanilla JS fetching /api/health, updating DOM, with a refresh button. Lint-clean.
• src/Web/HomePage/template.php: demo box (#yii3-vanilla-box).
• assets/main/site.css: styles for the demo box/badge/button.

Verification

• GET /api/health returns 200 JSON {status, framework, frontend, time}.
• Homepage renders the demo box; <script src="/assets/main/<hash>/app.js"> and <link .../site.css> are emitted automatically.
• phpstan analyse src config --level=5 → no errors.

Note / question for reviewers

While building this I hit WebViewRenderer::render('') throwing "The view path is not set" when trying to return a raw JSON response. This PR uses ResponseFactoryInterface instead. Should the template/docs recommend ResponseFactoryInterface for JSON APIs, and/or should WebViewRenderer allow an empty view path for API actions? (Tracked in #478 and discussions/479.)

How to test

php yii serve 0.0.0.0:8094 --docroot=public
# open http://127.0.0.1:8094/  -> Vanilla JS box loads status from the API

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on this repository. Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 00e7141e-a9be-4a76-80b2-a958e2e991e2

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

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

[codecov]

Codecov Report

❌ Patch coverage is 0% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.17%. Comparing base (db67e2e) to head (b8725f8).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/Web/Api/HealthAction.php	0.00%	16 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #480      +/-   ##
============================================
- Coverage     85.08%   78.17%   -6.92%     
- Complexity       29       31       +2     
============================================
  Files            11       12       +1     
  Lines           181      197      +16     
============================================
  Hits            154      154              
- Misses           27       43      +16     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.