fix(channels-intelligence): refuse an ephemeral post that names no recipient

An empty user id passed the truthiness guard, so the post went out to this
turn's own recipient and reported success for a recipient the caller never
identified. Comparing the requested id with the recipient directly refuses it
alongside a request naming somebody else.

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

packages/channels-intelligence/src/delivery-adapter-ephemeral.test.ts

@@ -96,6 +96,25 @@ describe("DeliveryAdapter ephemeral posts", () => {
     expect(effect).not.toHaveBeenCalled();
   });
 
+  it("refuses a request that names no recipient at all", async () => {
+    const effect = vi.fn(async () => ({}));
+    const session = { effect } as unknown as ClaimedChannelDelivery;
+    const managed = adapter() as PlatformAdapter;
+
+    // An empty user id identifies nobody, so it cannot agree with this turn's
+    // recipient — sending anyway would report success for a turn the caller
+    // never named.
+    await expect(
+      managed.postEphemeral?.(
+        { claimedDelivery: session, delivery: delivery() },
+        "",
+        [{ type: "text", props: { value: "Only you can see this" } }],
+        { fallbackToDM: true },
+      ),
+    ).resolves.toMatchObject({ ok: false });
+    expect(effect).not.toHaveBeenCalled();
+  });
+
   it("refuses a turn with no identified recipient", async () => {
     const effect = vi.fn(async () => ({}));
     const session = { effect } as unknown as ClaimedChannelDelivery;

packages/channels-intelligence/src/delivery-adapter.ts

@@ -334,7 +334,7 @@ export class DeliveryAdapter implements PlatformAdapter {
     if (!recipient) {
       return { ok: false, error: "This turn has no identified recipient" };
     }
-    if (requested && requested !== recipient) {
+    if (requested !== recipient) {
       return {
         ok: false,
         error: `A managed ephemeral message reaches only this turn's own recipient (${recipient})`,