Replace / with - for operation IDs (#660)

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## Motivation and Context
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Follow up from #658 addressing the feedback from @tadasant 

## How Has This Been Tested?
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tested? -->

## Breaking Changes
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## Types of changes
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the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update

## Checklist
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- [ ] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [ ] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed

## Additional context
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Signed-off-by: Radoslav Dimitrov <radoslav@stacklok.com>

internal/api/handlers/v0/auth/github_at.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"net/http"
 	"regexp"
+	"strings"
 
 	"github.com/danielgtaylor/huma/v2"
 	v0 "github.com/modelcontextprotocol/registry/internal/api/handlers/v0"
@@ -48,7 +49,7 @@ func RegisterGitHubATEndpoint(api huma.API, pathPrefix string, cfg *config.Confi
 
 	// GitHub token exchange endpoint
 	huma.Register(api, huma.Operation{
-		OperationID: "exchange-github-token" + pathPrefix,
+		OperationID: "exchange-github-token" + strings.ReplaceAll(pathPrefix, "/", "-"),
 		Method:      http.MethodPost,
 		Path:        pathPrefix + "/auth/github-at",
 		Summary:     "Exchange GitHub OAuth access token for Registry JWT",