ci: test MCP server module

[eshaffer321]

Summary

• Run the nested cmd/mcp-server module tests in CI
• Tidy cmd/mcp-server/go.sum so the nested module is reproducible

Test plan

• go test ./...
• (cd cmd/mcp-server && go test ./...)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 48.86%. Comparing base (eed1eb3) to head (4725ed7).

❌ Your project check has failed because the head coverage (48.86%) is below the target coverage (70.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #23   +/-   ##
=======================================
  Coverage   48.86%   48.86%           
=======================================
  Files          17       17           
  Lines        2032     2032           
=======================================
  Hits          993      993           
  Misses        953      953           
  Partials       86       86           

Flag	Coverage Δ
unittests	48.86% <ø> (ø)

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