fix: log full deterministic step output on failure for cloud visibility

[khaliqgant]

Summary

• Log the command being run for every deterministic step
• On failure, log full stdout/stderr via this.log() before throwing — lands in runner.log and is visible in agent-relay cloud logs
• Covers both code paths: executor (cloud/Daytona) and local spawn

Problem

When a deterministic step fails in cloud, the user sees only:

Step "compile" failed: Command failed with exit code 1

The actual error output is truncated to 500 chars in the exception message and never written to runner.log, making cloud failures opaque.

After this fix

[workflow 00:01] [compile] Running: npm run build
[workflow 00:02] [compile] Command failed (exit code 1)
[workflow 00:02] [compile] stderr:
src/index.ts(42,5): error TS2322: Type 'string' is not assignable to type 'number'.

Test plan

• Run a cloud workflow with a deterministic step that fails — full output now visible in agent-relay cloud logs
• Run locally with a failing deterministic step — same improvement in terminal output

🤖 Generated with Claude Code

---

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 2 additional findings.