fix: thread accountId through subagent announce

Co-authored-by: Adam Holt <adam91holt@users.noreply.github.com>

src/commands/agent/delivery.ts

@@ -48,13 +48,19 @@ export async function deliverAgentCommandResult(params: {
 
   const targetMode: ChannelOutboundTargetMode =
     opts.deliveryTargetMode ?? (opts.to ? "explicit" : "implicit");
+  const resolvedAccountId =
+    typeof opts.accountId === "string" && opts.accountId.trim()
+      ? opts.accountId.trim()
+      : targetMode === "implicit"
+        ? sessionEntry?.lastAccountId
+        : undefined;
   const resolvedTarget =
     deliver && isDeliveryChannelKnown && deliveryChannel
       ? resolveOutboundTarget({
           channel: deliveryChannel,
           to: opts.to,
           cfg,
-          accountId: targetMode === "implicit" ? sessionEntry?.lastAccountId : undefined,
+          accountId: resolvedAccountId,
           mode: targetMode,
         })
       : null;
@@ -112,6 +118,7 @@ export async function deliverAgentCommandResult(params: {
         cfg,
         channel: deliveryChannel,
         to: deliveryTarget,
+        accountId: resolvedAccountId,
         payloads: deliveryPayloads,
         bestEffort: bestEffortDeliver,
         onError: (err) => logDeliveryError(err),