Use ProcessSpec for invoking dotnet publish

[mitchdenny]

This should fix apparent hangs when doing aspire publish. The root issue was that when the process stdout buffer filled up the process would stop. This resolves that issue by reading out of that buffer as lines are written and piping them to stdout.

We already do this for docker build but hadn't yet done it to dotnet publish.

Fixes: #9233

[Copilot]

Pull Request Overview

This PR addresses apparent hangs during dotnet publish by updating the process invocation to use ProcessSpec for streaming output and error data.

• Replace ProcessStartInfo with ProcessSpec and its callbacks to prevent stdout buffer blockage.
• Adjust the return type of BuildProjectContainerImageAsync and update PublishCommand's activity loop condition.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/Aspire.Hosting/Publishing/ResourceContainerImageBuilder.cs	Updated dotnet publish logic to stream process output and removed the string return value.
src/Aspire.Cli/Commands/PublishCommand.cs	Modified the publishing activities termination condition logic.

Comments suppressed due to low confidence (2)

src/Aspire.Hosting/Publishing/ResourceContainerImageBuilder.cs:74

• The method signature has changed from returning a string to void. Please verify that all callers of BuildProjectContainerImageAsync are updated to reflect this change and that any dependencies on its return value are addressed.

private async Task BuildProjectContainerImageAsync(IResource resource, CancellationToken cancellationToken)

src/Aspire.Cli/Commands/PublishCommand.cs:232

• The updated return condition now depends on all activities being free of errors. Confirm that this logic accurately reflects the intended termination criteria for processing publishing activities.

return lastActivityUpdateLookup.All(kvp => !kvp.Value.IsError);

[davidfowl]

/backport to release/9.3

[github-actions]

Started backporting to release/9.3: https://github.com/dotnet/aspire/actions/runs/15327499000