test: cover server analyzer mode

[mgalore]

Summary

• add integration coverage for analyzerMode: "server" on Webpack 4 and 5
• verify the server listens on an automatically allocated port and receives the configured URL callback
• close HTTP and WebSocket servers after each test to avoid leaked handles

Closes #727

Verification

• npm run test:coverage
• npm run lint
• npm run build
• git diff --check

[changeset-bot]

⚠️ No Changeset found

Latest commit: d83ad8c

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[linux-foundation-easycla]

• ❌ - login: @mgalore / name: Jonathan Amponsah. The commit (d83ad8c) is not authorized under a signed CLA. Please click here to be authorized. For further assistance with EasyCLA, please visit our EasyCLA portal and chat with our support bot.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.90%. Comparing base (83a8ee5) to head (d83ad8c).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #729      +/-   ##
==========================================
+ Coverage   76.29%   76.90%   +0.61%     
==========================================
  Files          17       17              
  Lines         983      983              
  Branches      358      358              
==========================================
+ Hits          750      756       +6     
+ Misses        206      201       -5     
+ Partials       27       26       -1     

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