feat(cron): add --account flag for multi-account delivery routing (#26284)

* feat(cron): add --account flag for multi-account delivery routing

Add support for explicit delivery account routing in cron jobs across CLI, normalization, delivery planning, and isolated delivery target resolution.

Highlights:
- Add --account <id> to cron add and cron edit
- Add optional delivery.accountId to cron types and delivery plan
- Normalize and trim delivery.accountId in cron create/update normalization
- Prefer explicit accountId over session lastAccountId and bindings fallback
- Thread accountId through isolated cron run delivery resolution
- Preserve cron edit --best-effort-deliver/--no-best-effort-deliver behavior by keeping implicit announce mode
- Expand tests for account passthrough/merge/precedence and CLI account flows

* cron: resolve rebase duplicate accountId fields

---------

Co-authored-by: Tak Hoffman <781889+Takhoffman@users.noreply.github.com>

src/cron/service/jobs.ts

@@ -609,6 +609,7 @@ function mergeCronDelivery(
     mode: existing?.mode ?? "none",
     channel: existing?.channel,
     to: existing?.to,
+    accountId: existing?.accountId,
     bestEffort: existing?.bestEffort,
   };
 
@@ -623,6 +624,10 @@ function mergeCronDelivery(
     const to = typeof patch.to === "string" ? patch.to.trim() : "";
     next.to = to ? to : undefined;
   }
+  if ("accountId" in patch) {
+    const accountId = typeof patch.accountId === "string" ? patch.accountId.trim() : "";
+    next.accountId = accountId ? accountId : undefined;
+  }
   if (typeof patch.bestEffort === "boolean") {
     next.bestEffort = patch.bestEffort;
   }