test(media-dedup): add missing coverage for Discord media dedup wiring

Cover three integration points where media dedup could silently regress:
- trimMessagingToolSent FIFO cap at 200 entries
- buildReplyPayloads media filter wiring (new test file)
- followup-runner messagingToolSentMediaUrls filtering

src/auto-reply/reply/followup-runner.test.ts

@@ -257,6 +257,47 @@ describe("createFollowupRunner messaging tool dedupe", () => {
     expect(onBlockReply).not.toHaveBeenCalled();
   });
 
+  it("drops media URL from payload when messaging tool already sent it", async () => {
+    const onBlockReply = vi.fn(async () => {});
+    runEmbeddedPiAgentMock.mockResolvedValueOnce({
+      payloads: [{ mediaUrl: "/tmp/img.png" }],
+      messagingToolSentMediaUrls: ["/tmp/img.png"],
+      meta: {},
+    });
+
+    const runner = createFollowupRunner({
+      opts: { onBlockReply },
+      typing: createMockTypingController(),
+      typingMode: "instant",
+      defaultModel: "anthropic/claude-opus-4-5",
+    });
+
+    await runner(baseQueuedRun());
+
+    // Media stripped → payload becomes non-renderable → not delivered.
+    expect(onBlockReply).not.toHaveBeenCalled();
+  });
+
+  it("delivers media payload when not a duplicate", async () => {
+    const onBlockReply = vi.fn(async () => {});
+    runEmbeddedPiAgentMock.mockResolvedValueOnce({
+      payloads: [{ mediaUrl: "/tmp/img.png" }],
+      messagingToolSentMediaUrls: ["/tmp/other.png"],
+      meta: {},
+    });
+
+    const runner = createFollowupRunner({
+      opts: { onBlockReply },
+      typing: createMockTypingController(),
+      typingMode: "instant",
+      defaultModel: "anthropic/claude-opus-4-5",
+    });
+
+    await runner(baseQueuedRun());
+
+    expect(onBlockReply).toHaveBeenCalledTimes(1);
+  });
+
   it("persists usage even when replies are suppressed", async () => {
     const storePath = path.join(
       await fs.mkdtemp(path.join(tmpdir(), "openclaw-followup-usage-")),