recipe-runner does not stream nested agent progress or sub-recipe failure details

[rysweet]

Summary

Recipe-runner/default-workflow execution currently provides very poor live observability for nested agent steps. The top-level tmux/log stayed blank for long stretches even while nested claude -p agents were actively running.

Reproduction

While debugging qa-team workflow remediation:

• /tmp/recipe-1773153352.log stayed empty during nested agent execution
• tmux capture-pane also stayed blank
• The only way to understand progress was to inspect the process tree and use lsof to discover ephemeral .recipe-output/agent-step-*.log files
• Those step log files were also zero bytes during execution

Expected

• Top-level recipe logs should stream meaningful progress from nested agent steps
• Failures in sub-recipes should include enough detail to diagnose the blocker without process spelunking

Actual

• Long-running workflow steps look hung
• Failure details are only summarized at the end
• Nested sub-recipe failures are hard to debug in real time

Suggested Fix

• Stream agent step progress into the parent recipe log
• Emit step start/finish markers and child log paths
• Preserve sub-recipe failure details in the parent failure output
• Consider a --verbose mode that always surfaces nested logs

Impact

• Debugging recipe failures is much slower than it should be
• Users may assume the workflow is hung
• Operators have to use low-level process inspection just to see what is happening