docs(server): explain why the seed's issue idempotency key is not revision-scoped

Cloud's reconcile runs off portfolio fetches, which can overlap, so two
pushes of the same revision can race. The idempotency key on the first
task is what makes that safe. It is deliberately company-scoped rather
than revision-scoped, so that a later revision still dedupes against
whatever the first push created if the recorded issue id is lost. That
reasoning was not obvious from the call site.

Co-authored-by: Paperclip <noreply@paperclip.ing>
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

server/src/services/onboarding-seed.ts

@@ -233,6 +233,11 @@ export function onboardingSeedService(db: Db) {
         });
       } else {
         const projectId = await resolveOnboardingProjectId(companyId, goalId);
+        // The idempotency key is what protects two pushes that arrive at once
+        // — Cloud's reconcile runs off portfolio fetches, which can overlap.
+        // It is deliberately not revision-scoped: if the recorded issue is
+        // lost, a later revision should still dedupe against whatever the
+        // first push created.
         const created = await issueSvc.create(companyId, {
           title: firstTaskTitle,
           ...(firstTaskDetails ? { description: firstTaskDetails } : {}),