fix(outbound): fail media-only text-only adapter fallback

src/infra/outbound/deliver.test.ts

@@ -971,6 +971,53 @@ describe("deliverOutboundPayloads", () => {
     expect(results).toEqual([{ channel: "matrix", messageId: "mx-2" }]);
   });
 
+  it("fails media-only payloads when plugin outbound omits sendMedia", async () => {
+    hookMocks.runner.hasHooks.mockReturnValue(true);
+    const sendText = vi.fn().mockResolvedValue({ channel: "matrix", messageId: "mx-3" });
+    setActivePluginRegistry(
+      createTestRegistry([
+        {
+          pluginId: "matrix",
+          source: "test",
+          plugin: createOutboundTestPlugin({
+            id: "matrix",
+            outbound: { deliveryMode: "direct", sendText },
+          }),
+        },
+      ]),
+    );
+
+    await expect(
+      deliverOutboundPayloads({
+        cfg: {},
+        channel: "matrix",
+        to: "!room:1",
+        payloads: [{ text: "   ", mediaUrl: "https://example.com/file.png" }],
+      }),
+    ).rejects.toThrow(
+      "Plugin outbound adapter does not implement sendMedia and no text fallback is available for media payload",
+    );
+
+    expect(sendText).not.toHaveBeenCalled();
+    expect(logMocks.warn).toHaveBeenCalledWith(
+      "Plugin outbound adapter does not implement sendMedia; media URLs will be dropped and text fallback will be used",
+      expect.objectContaining({
+        channel: "matrix",
+        mediaCount: 1,
+      }),
+    );
+    expect(hookMocks.runner.runMessageSent).toHaveBeenCalledWith(
+      expect.objectContaining({
+        to: "!room:1",
+        content: "",
+        success: false,
+        error:
+          "Plugin outbound adapter does not implement sendMedia and no text fallback is available for media payload",
+      }),
+      expect.objectContaining({ channelId: "matrix" }),
+    );
+  });
+
   it("emits message_sent failure when delivery errors", async () => {
     hookMocks.runner.hasHooks.mockReturnValue(true);
     const sendWhatsApp = vi.fn().mockRejectedValue(new Error("downstream failed"));

src/infra/outbound/deliver.ts

@@ -750,7 +750,9 @@ async function deliverOutboundPayloadsCore(
         );
         const fallbackText = payloadSummary.text.trim();
         if (!fallbackText) {
-          continue;
+          throw new Error(
+            "Plugin outbound adapter does not implement sendMedia and no text fallback is available for media payload",
+          );
         }
         const beforeCount = results.length;
         await sendTextChunks(fallbackText, sendOverrides);