Address WSS discovery review feedback and follow-up tests

[Copilot]

Description

Addresses the review feedback for application-aware WSS discovery and incorporates the follow-up coverage from #4179.

• Observe the returned task when asserting null ApplicationConfiguration validation with Assert.ThrowsAsync.
• Correct the discovery URL comment grammar.
• Verify WSS discovery uses the application's certificate validator by rejecting an untrusted discovery certificate and asserting the TLS authentication failure.
• Connect the anonymous WSS binary test through the discovered ConfiguredEndpoint, then verify the selected transport profile and security mode.

Related Issues

• Supersedes Superseded by #4178 #4179.

Checklist

• I have signed the CLA and read the CONTRIBUTING doc.
• I have added tests that prove my fix is effective or that my feature works and increased code coverage.
• I have added all necessary documentation.
• I have verified that my changes do not introduce (new) build or analyzer warnings.
• I ran all tests locally using the UA.slnx solution against at least .net framework and .net 10, and all passed.
• I fixed all failing and flaky tests in the CI pipelines and all CodeQL warnings.
• I have addressed all PR feedback received.

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✅ o6-jpfr
❌ Copilot
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[marcschier]

@copilot fix conflicts with master, then merge #4179 into this and update PR title and description. Close #4179 when done

[Copilot]

Pull request overview

This PR addresses prior review feedback around application-aware WSS discovery by fixing an async exception assertion in tests and cleaning up a small grammar issue in a discovery-URL comment.

Changes:

• Update the ConfiguredEndpointTests null-configuration assertion to use Assert.ThrowsAsync so the returned task is properly observed.
• Fix grammar in an inline comment in ConfiguredEndpoints.UpdateFromServerCoreAsync related to discovery URL handling.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
tests/Opc.Ua.Core.Tests/Stack/Client/ConfiguredEndpointTests.cs	Switches the null ApplicationConfiguration validation test to Assert.ThrowsAsync for correct async exception testing.
src/Opc.Ua.Core/Stack/Configuration/ConfiguredEndpoints.cs	Minor grammar correction in a discovery URL comment within the server update path.

[Copilot]

@copilot fix conflicts with master, then merge #4179 into this and update PR title and description. Close #4179 when done

Merged current master and the latest #4179 head into #4178 as true merge commits, then updated #4178's title and description. The affected net10.0 test suites pass (4,145 Core and 777 Sessions tests), and both affected projects build cleanly for net48. I also marked #4179 as superseded; the GitHub write API is currently refusing to close that draft PR because it cannot resolve the PR node, so #4179 still needs to be closed manually.