Pipeline step summary doesn't render errors clearly

## Description

The pipeline step summary (introduced in #15530) doesn't render well when steps have errors. When a compose deploy step fails, the error message is not clearly visible in the step summary timeline output.

## Steps to Reproduce

1. Run `aspire deploy` with a Docker Compose environment
2. Have a step fail (e.g., compose up fails due to a missing container runtime)
3. Observe the step summary output

## Expected Behavior

The error message should be clearly visible and readable in the summary output, making it easy to diagnose what went wrong.

## Actual Behavior

The error rendering in the step summary is not clear — the failure reason is hard to spot in the timeline output.

## Additional Context

- Related PR: #15530 (Render publish summary hierarchy and timeline)
- Discovered while testing Podman container runtime support for Docker Compose deploy
- Screenshot to follow in comments

/cc @sebastienros