[P3] Preserve optional process.off compatibility in getProcessDeps

[Keegs12]

Found while auditing Stack #633 (#628–#633); this also matches the unresolved review thread on PR #633.

Problem

ProcessDeps.offSignal and ProcessLike.off are typed as optional, and ProcessPlatformAdapter.removeSignalHandlers() already uses optional chaining. However, getProcessDeps() now rejects the runtime unless processLike.off exists:

if (!processLike?.env || !processLike.on || !processLike.off || !processLike.exit || !cryptoLike?.randomUUID) {
  throw new Error('Process runtime is not available');
}

That makes the optional contract unreachable for Node/Bun-compatible process shims or older runtimes that provide on but not off, and it turns what could be a cleanup limitation into a startup failure.

Relevant code:

• pkgs/edge-worker/src/platform/processDeps.ts:28-41
• pkgs/edge-worker/src/platform/ProcessPlatformAdapter.ts:151-160

Suggested fix

Remove !processLike.off from the required-runtime check and construct offSignal only when processLike.off is present. Add a unit test with a process-like object that has on but no off, verifying dependency creation and worker startup still work.

[jumski]

hey @Keegs12 thanks for checking out pgflow - do you need to host workers outside supabase? im sitting on this stack for some time and close to releasing it and any help with testing it or providing feedback would be extremely useful!