Fix incorrect Content-Length for swagger-ui and Redoc static assets

[martincostello]

• Fix incorrect length value being stored when embedded resources are not served compressed.
• Extend integration tests to verify that the stream is the same length as the Content-Length header.

Fixes #3486 and #3487.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.91%. Comparing base (577db5f) to head (413e3e0).

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3488   +/-   ##
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  Coverage   93.91%   93.91%           
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  Files         110      110           
  Lines        3810     3810           
  Branches      723      723           
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  Hits         3578     3578           
  Misses        232      232           

Flag	Coverage Δ
Linux	93.91% <100.00%> (ø)
Windows	93.91% <100.00%> (ø)
macOS	93.91% <100.00%> (ø)

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[Copilot]

Pull Request Overview

This PR ensures the Content-Length header reflects the actual length of embedded static assets by fixing the provider logic and adding test assertions.

• Update EmbeddedResourceProvider to set DecompressedLength correctly
• Add assertions in Swagger UI and ReDoc integration tests to verify Content-Length matches the returned stream length

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
test/Swashbuckle.AspNetCore.IntegrationTests/SwaggerUIIntegrationTests.cs	Added Assert.Equal(response.Content.Headers.ContentLength, actual.Length) to both decompressed and GZip tests
test/Swashbuckle.AspNetCore.IntegrationTests/ReDocIntegrationTests.cs	Added Assert.Equal(response.Content.Headers.ContentLength, actual.Length) to both decompressed and GZip tests
src/Shared/EmbeddedResourceProvider.cs	Changed entry.DecompressedLength to use decompressed.Length instead of content.Length

Comments suppressed due to low confidence (1)

src/Shared/EmbeddedResourceProvider.cs:154

• [nitpick] Add a brief comment explaining why DecompressedLength should use decompressed.Length (the full uncompressed size) to aid future maintainers in understanding this assignment.

            entry.DecompressedLength = decompressed.Length;