chore(deps): support libopenapi v0.41.1

[mcstepp]

Summary

Updates libopenapi from v0.38.6 to v0.41.1.

Changes

• YAML import swap: libopenapi v0.41.1 now uses github.com/pb33f/go-yaml instead of go.yaml.in/yaml/v4, and mixing the two causes type errors. This PR updates every import to the new package. The package name is still yaml, so no other code changed.
• Schemas that $ref another file: in v0.41.1, a component schema that is just a $ref to another file reports that file's index from GoLow().GetIndex(). Its root node is still the $ref node in the file that contains it. buildSchemaDocumentResources was searching the wrong file and failing with schema node was not found in its root document. The new locateSchemaRootNodeIndex checks the schema's own index first, then the other loaded files, to find the one that contains the node. This restores the v0.38.6 behavior.
• Go 1.26: libopenapi v0.41.1 declares go 1.26.0, so go.mod now does too. CI now runs the build job on Go 1.26 and golangci-lint v2.12, because v2.8 won't lint a module that targets a newer Go version.

⚠️ Breaking

Anyone using this module now needs Go 1.26 or later, because libopenapi v0.41.1 requires it.

Testing

• go build ./..., go vet ./... and go test -race ./... pass
• golangci-lint v2.12.2 reports 0 issues
• New test covers the case where the node isn't found in the schema's index and no other files are loaded
• schema_validation coverage unchanged: 99.4%

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.27%. Comparing base (f309f59) to head (141bc89).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #325   +/-   ##
=======================================
  Coverage   98.27%   98.27%           
=======================================
  Files          75       75           
  Lines        9192     9205   +13     
=======================================
+ Hits         9033     9046   +13     
  Misses        132      132           
  Partials       27       27           

Flag	Coverage Δ
unittests	98.27% <100.00%> (+<0.01%)	⬆️

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[mcstepp]

Sorry! Didn't see your PR #324

I'll close mine