Fix NotSupportedException in ResourceLoggerService.WatchAnySubscribersAsync disposal

[Copilot]

Description

WatchAnySubscribersAsync was throwing NotSupportedException when the async enumerator was disposed. The method subscribed to nested events (LoggerAdded → OnSubscribersChanged) but only cleaned up the outer subscription in the finally block, leaving inner event handlers dangling.

Changes:

• Track all OnSubscribersChanged event handler subscriptions in a list
• Unsubscribe from all tracked handlers in the finally block before completing the channel

// Before: Lambda subscription was never cleaned up
state.OnSubscribersChanged += (hasSubscribers) => { ... };

// After: Handler is tracked and explicitly unsubscribed
Action<bool> handler = (hasSubscribers) => { ... };
state.OnSubscribersChanged += handler;
subscribedStates.Add((state, handler));
// ... later in finally block ...
foreach (var (state, handler) in subscribedStates)
{
    state.OnSubscribersChanged -= handler;
}

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
  • No
• Does the change make any security assumptions or guarantees?
  • Yes
  • No
• Does the change require an update in our Aspire docs?
  • Yes
  • No

Original prompt

Investigate ths:

System.NotSupportedException : Specified method is not supported. at Aspire.Hosting.ApplicationModel.ResourceLoggerService.WatchAnySubscribersAsync(CancellationToken cancellationToken)+System.IAsyncDisposable.DisposeAsync()
at Microsoft.AspNetCore.InternalTesting.AsyncTestHelpers.DefaultTimeout[T](IAsyncEnumerable1 asyncEnumerable, Int32 milliseconds, String filePath, Int32 lineNumber)+MoveNext() in /Users/runner/work/aspire/aspire/tests/Shared/AsyncTestHelpers.cs:line 60 at Microsoft.AspNetCore.InternalTesting.AsyncTestHelpers.DefaultTimeout[T](IAsyncEnumerable1 asyncEnumerable, Int32 milliseconds, String filePath, Int32 lineNumber)+System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult()
at Aspire.Hosting.Tests.Dashboard.DashboardLifecycleHookTests.WatchDashboardLogs_WrittenToHostLoggerFactory(Nullable1 timestamp, String logMessage, String expectedMessage, String expectedCategory, LogLevel expectedLevel) in /Users/runner/work/aspire/aspire/tests/Aspire.Hosting.Tests/Dashboard/DashboardLifecycleHookTests.cs:line 51 at Aspire.Hosting.Tests.Dashboard.DashboardLifecycleHookTests.WatchDashboardLogs_WrittenToHostLoggerFactory(Nullable1 timestamp, String logMessage, String expectedMessage, String expectedCategory, LogLevel expectedLevel) in /Users/runner/work/aspire/aspire/tests/Aspire.Hosting.Tests/Dashboard/DashboardLifecycleHookTests.cs:line 51
--- End of stack trace from previous location ---

StdOut

| [2025-12-18T18:08:40] Aspire.Hosting.ApplicationModel.ResourceNotificationService Trace: Version: 1 Resource aspire-dashboard/aspire-dashboard-qgvxmrva update published: ResourceType = Executable, CreationTimeStamp = (null), State = { Text = (null), Style = (null) }, IsHidden = True, HeathStatus = (null), ResourceReady = False, ExitCode = (null), Urls = { }, EnvironmentVariables = { }, Properties = { }, HealthReports = { }, Commands = { }

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[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 -- 13644

Or

• Run remotely in PowerShell:

iex "& { $(irm https://raw.githubusercontent.com/dotnet/aspire/main/eng/scripts/get-aspire-cli-pr.ps1) } 13644"