Retry or fail on dispatch failure

[jameskoll-whatnot]

Background

Errors when dispatching aren't handled well, leaving doomed workflows polling for results until the step times out. Example: https://github.com/Whatnot-Inc/whatnot_backend/actions/runs/28871267338/job/85636518486

Going for functional over perfection here, as this workflow will be a lot less important and maybe even unused in a post buildkite world

Changes

• Detect errors from dispatch response and
  • If it's a clear failure, immediately fail
  • If it's an ambiguous failure, retry once before failing
• Have claude rework the unit tests to switch from curl to gh mocking. This was changed in the previous PR contributed by blacksmith
• Have claude update unit tests to test for the new expected behaviors

Testing

• Vibe-coded unit tests which seem plausible
• Tested happy path here: https://github.com/Whatnot-Inc/argo-app-test/actions/runs/28897614072/job/85726325270