docs: document executable JAR service descriptor merging

[bednar]

Summary

• Document that executable JAR packaging must merge META-INF/services files for the query API.
• Add the common NameResolver 'unix' error users may see when service descriptors are overwritten.
• Show the Maven Shade ServicesResourceTransformer fix.

Validation

• mvn -q -DskipTests package
• git diff --check

Related to #404.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.73%. Comparing base (2628f6e) to head (c4320e8).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #406   +/-   ##
=======================================
  Coverage   88.73%   88.73%           
=======================================
  Files          21       21           
  Lines        1553     1553           
  Branches      281      281           
=======================================
  Hits         1378     1378           
  Misses         77       77           
  Partials       98       98           

☔ 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.

[karel-rehor]

Looks good to me. 🚴 🏁