fix: normalize subagent announce delivery origin

Co-authored-by: Adam Holt <mail@adamholt.co.nz>

src/utils/delivery-context.test.ts

@@ -0,0 +1,45 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  deliveryContextKey,
+  mergeDeliveryContext,
+  normalizeDeliveryContext,
+} from "./delivery-context.js";
+
+describe("delivery context helpers", () => {
+  it("normalizes channel/to/accountId and drops empty contexts", () => {
+    expect(
+      normalizeDeliveryContext({
+        channel: " whatsapp ",
+        to: " +1555 ",
+        accountId: " acct-1 ",
+      }),
+    ).toEqual({
+      channel: "whatsapp",
+      to: "+1555",
+      accountId: "acct-1",
+    });
+
+    expect(normalizeDeliveryContext({ channel: "  " })).toBeUndefined();
+  });
+
+  it("merges primary values over fallback", () => {
+    const merged = mergeDeliveryContext(
+      { channel: "whatsapp", to: "channel:abc" },
+      { channel: "slack", to: "channel:def", accountId: "acct" },
+    );
+
+    expect(merged).toEqual({
+      channel: "whatsapp",
+      to: "channel:abc",
+      accountId: "acct",
+    });
+  });
+
+  it("builds stable keys only when channel and to are present", () => {
+    expect(deliveryContextKey({ channel: "whatsapp", to: "+1555" })).toBe(
+      "whatsapp|+1555|",
+    );
+    expect(deliveryContextKey({ channel: "whatsapp" })).toBeUndefined();
+  });
+});

src/utils/delivery-context.ts

@@ -18,3 +18,23 @@ export function normalizeDeliveryContext(context?: DeliveryContext): DeliveryCon
     accountId,
   };
 }
+
+export function mergeDeliveryContext(
+  primary?: DeliveryContext,
+  fallback?: DeliveryContext,
+): DeliveryContext | undefined {
+  const normalizedPrimary = normalizeDeliveryContext(primary);
+  const normalizedFallback = normalizeDeliveryContext(fallback);
+  if (!normalizedPrimary && !normalizedFallback) return undefined;
+  return normalizeDeliveryContext({
+    channel: normalizedPrimary?.channel ?? normalizedFallback?.channel,
+    to: normalizedPrimary?.to ?? normalizedFallback?.to,
+    accountId: normalizedPrimary?.accountId ?? normalizedFallback?.accountId,
+  });
+}
+
+export function deliveryContextKey(context?: DeliveryContext): string | undefined {
+  const normalized = normalizeDeliveryContext(context);
+  if (!normalized?.channel || !normalized?.to) return undefined;
+  return `${normalized.channel}|${normalized.to}|${normalized.accountId ?? ""}`;
+}