gateway transformation run reports success for thrown errors, invalid JS, and unknown IDs

[leggetter]

Summary

gateway transformation run reports success and returns {} for every kind of failure — a thrown exception, invalid JavaScript, or a transformation ID that does not exist. Testing a transformation before shipping it is the command's entire purpose, and it cannot tell you when the transformation is broken.

Reproduce

hookdeck gateway transformation run \
  --code 'addHandler("transform",(r,c)=>{ throw new Error("boom"); });' \
  --request '{"headers":{}}' --output json
→ {}
→ exit 0

Without --output json:

✔ Transformation run completed
→ exit 0

Identical {} and exit 0 for:

• a nonexistent transformation: --id trs_bogus000
• syntactically invalid JavaScript

console.log output from the transformation is also not surfaced.

Expected

The runtime or compile error should be reported, and the exit code should be non-zero. A nonexistent --id should say so. Console output should be shown — it is the main way people debug a transform.

Scope

Pre-existing, not a regression. Verified identical on fbb924a (pre-#392) and on the merged branch.

Why it matters

This is the local-testing command. Someone iterating on a transformation gets a green tick whether their code works or throws, so the failure surfaces later in production delivery instead. It is the same shape as #367's note about outpost attempt get hiding the failure reason — "finding out why a delivery failed is the entire reason to run this command" — but on a different command, so filing separately.

Related

• CLI output and error-reporting papercuts found in pre-release testing #367 — CLI output and error-reporting papercuts (same shape, different command)

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Filed by Claude on Phil's behalf, from release-candidate regression testing.