Fix OpenTelemetry SchemaURL conflicts

[raphael]

Summary

• Stop setting a resource schema URL in clue.NewConfig by using resource.NewSchemaless.

Rationale

resource.Default() (from the OTel SDK) and clue's service resource were using different schema URLs, which can cause the SDK to fail fast with a conflicting schema URL error during resource.Merge. Building the service resource schemaless avoids schema conflicts while keeping the semantic attributes.

Test plan

• go test ./...

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.95%. Comparing base (898dc7f) to head (662b307).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #642      +/-   ##
==========================================
- Coverage   86.95%   86.95%   -0.01%     
==========================================
  Files          39       39              
  Lines        2009     2008       -1     
==========================================
- Hits         1747     1746       -1     
  Misses        238      238              
  Partials       24       24              

Flag	Coverage Δ
micro	86.95% <100.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 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.