Fix infinite queue retry loop for cancelled workflow runs

[gdaybrice]

Summary

• The step execution catch block (step-handler.ts) only handled 410 Gone (completed runs) but not 409 Conflict (cancelled/terminal runs)
• When a step failed on a cancelled run, the step_retrying event also returned 409, which was uncaught — causing the queue to retry the message indefinitely
• Fix: handle 409 the same way 410 is already handled — log and return early

Context

Observed in production: a cancelled workflow run (wrun_01KH4WFCWWHVRK9331EX49EMQH) triggered 99+ queue retries in ~18 hours with no sign of stopping.

Queue callback error: Error [WorkflowAPIError]: Cannot step_retrying workflow run wrun_01KH4WFCWWHVRK9331EX49EMQH because it has already finished with status 'cancelled'
    at async default (.next/server/chunks/_381bce51._.js:180:8345)
    at async db.processMessage (.next/server/chunks/_381bce51._.js:173:15814)
    at async db.consume (.next/server/chunks/_381bce51._.js:173:16538) {
  cause: undefined,
  status: 409,
  code: undefined,
  url: 'https://vercel-workflow.com/api/v2/runs/wrun_01KH4WFCWWHVRK9331EX49EMQH/events'
}

[changeset-bot]

🦋 Changeset detected

Latest commit: d7f6d47

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 14 packages

Name	Type
@workflow/core	Patch
@workflow/builders	Patch
@workflow/cli	Patch
@workflow/next	Patch
@workflow/nitro	Patch
@workflow/web-shared	Patch
workflow	Patch
@workflow/astro	Patch
@workflow/nest	Patch
@workflow/rollup	Patch
@workflow/sveltekit	Patch
@workflow/vite	Patch
@workflow/world-testing	Patch
@workflow/nuxt	Patch

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