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/normalize.ts

@@ -183,6 +183,16 @@ function coerceDelivery(delivery: UnknownRecord) {
       delete next.to;
     }
   }
+  if (typeof delivery.accountId === "string") {
+    const trimmed = delivery.accountId.trim();
+    if (trimmed) {
+      next.accountId = trimmed;
+    } else {
+      delete next.accountId;
+    }
+  } else if ("accountId" in next && typeof next.accountId !== "string") {
+    delete next.accountId;
+  }
   return next;
 }