fix: preserve Nitro workflow step registration side effects

[comfuture]

Summary

• side-effect import generated Nitro workflow handler bundles before reading their POST export
• keep step registration side effects alive when Nitro bundles workflow/steps.mjs
• add a regression test for Nitro v2 and v3 virtual handlers

Why

In Nitro/Nuxt local production builds, the generated workflow/steps.mjs bundle can be treated as a pure export provider when the virtual handler only imports { POST }. That allows the step bundle's top-level registerStepFunction(...) calls to disappear from the final Nitro server bundle, which leads to runtime failures like Step \"...\" not found when a queued step executes.

Importing the generated bundle for side effects before consuming POST keeps the registration code in the final server output.

Validation

• pnpm vitest run packages/nitro/src/index.test.ts
• pnpm --filter @workflow/example-nuxt build
• confirmed the built Nuxt Nitro bundle contains registerStepFunction(...) calls for app steps after this change

[changeset-bot]

🦋 Changeset detected

Latest commit: a536418

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

This PR includes changesets to release 16 packages

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

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[pranaygp]

@VaguelySerious @pi0 what do you think?

[pi0]

LGTM if it is delibrate to even have side effects... Is there any backstory to this? (why we need side-effects?)

[VaguelySerious]

Hey @comfuture, could you ensure this check passes? And also add a comment as to what issue you were seeing concretely that was solved through this PR. Once that's done, we'll run e2e tests and merge the PR

[comfuture]

Hey @comfuture, could you ensure this check passes? And also add a comment as to what issue you were seeing concretely that was solved through this PR. Once that's done, we'll run e2e tests and merge the PR

Thanks. I fixed the check that was failing there; it was the DCO check, and it now passes.
The concrete issue I was seeing was in Nuxt + Nitro production builds when @workflow/nuxt was enabled.

In that setup, the generated workflow/steps.mjs module could be reduced to only importing POST, which meant the handler itself loaded, but the module’s top-level step registrations did not run. As a result, the app built successfully, but the workflow steps were missing at runtime after build.

This change keeps a bare import of the generated steps module so those registration side effects are preserved.

[pi0]

Just a note, next nitro v3 release will have less agressive tree-shaking config (currently available in nightly) worth to check if after we still need this fix or not. More info: nitrojs/nitro#4164

[VaguelySerious]

@pi0 Merged for now and will add a comment mentioning that this fix could maybe be reverted after nitrojs/nitro#4164