Improve flaky dashboard integration test

[JamesNK]

Description

I think some dashboard tests have been flaky because the next random port logic doesn't provide a min random number. A random increase of 0 could be used which would generate unexpected test results.

Checklist

• Is this feature complete?
  • Yes. Ready to ship.
  • No. Follow-up changes expected.
• Are you including unit tests for the changes and scenario tests if relevant?
  • Yes
  • No
• Did you add public API?
  • Yes
    • If yes, did you have an API Review for it?
      • Yes
      • No
    • Did you add <remarks /> and <code /> elements on your triple slash comments?
      • Yes
      • No
  • No
• Does the change make any security assumptions or guarantees?
  • Yes
    • If yes, have you done a threat model and had a security review?
      • Yes
      • No
  • No
• Does the change require an update in our Aspire docs?
  • Yes
    • Link to aspire-docs issue (consider using one of the following templates):
      • New (or update) doc-idea template
      • New breaking-change template
      • New diagnostic template
  • No

[github-actions]

🚀 Dogfood this PR with:

⚠️ WARNING: Do not do this without first carefully reviewing the code of this PR to satisfy yourself it is safe.

curl -fsSL https://raw.githubusercontent.com/dotnet/aspire/main/eng/scripts/get-aspire-cli-pr.sh | bash -s -- 12534

Or

• Run remotely in PowerShell:

iex "& { $(irm https://raw.githubusercontent.com/dotnet/aspire/main/eng/scripts/get-aspire-cli-pr.ps1) } 12534"

[Copilot]

Pull Request Overview

This PR enhances the LogOutput_LocalhostAddress_LocalhostInLogOutput test to improve reliability and add MCP endpoint logging verification. The test previously had issues with port allocation retries due to shared state between test sink instances.

• Modified test to reuse a single TestSink instance across retries instead of recreating it, preventing log pollution from previous failed attempts
• Added MCP endpoint configuration and verification to the test
• Improved port collision detection in ServerRetryHelper with better random spacing and duplicate detection

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
tests/Aspire.Dashboard.Tests/Integration/StartupTests.cs	Enhanced test to verify MCP endpoint logging, fixed TestSink reuse issue, and added OTLP HTTP port configuration
tests/Aspire.Dashboard.Tests/Integration/ServerRetryHelper.cs	Added duplicate port detection and improved random port spacing
src/Aspire.Dashboard/DashboardWebApplication.cs	Added MCP endpoint logging to startup output

[JamesNK]

/backport to release/13.0

[github-actions]

Started backporting to release/13.0: https://github.com/dotnet/aspire/actions/runs/18962795178