CB-307 Increment 3: bridge_ack tool — per-msgId ack refinement

- MessageService.ackReply(target, msgId) delegates to inbox.ack
- BridgeMcp registers bridge_ack tool with target/msgId args
- Tests: valid/invalid args, ack surface via BridgeMcp

bridged/src/test/java/dev/ltms/bridged/mcp/BridgeMcpTest.java

@@ -303,6 +303,37 @@ class BridgeMcpTest {
                 sessionManager(h, "http://gx00.gw:8000", Set.of("gx00.gw")), "  ").isError());
     }
 
+    @Test
+    void bridgeAckReturnsConfirmationForValidArgs() {
+        McpSchema.CallToolResult res = BridgeMcp.ack(messages, "term_a", "msg-1");
+        assertNotEquals(Boolean.TRUE, res.isError());
+        assertTrue(textOf(res).contains("msg-1"), "response should mention the msgId");
+    }
+
+    @Test
+    void bridgeAckRejectsMissingArgs() {
+        assertTrue(BridgeMcp.ack(messages, null, "msg-1").isError());
+        assertTrue(BridgeMcp.ack(messages, "term_a", null).isError());
+        assertTrue(BridgeMcp.ack(messages, "  ", "msg-1").isError());
+    }
+
+    @Test
+    void bridgeAckRemovesSpecificReply() {
+        // Queue a reply and capture its msgId.
+        BridgeMcp.reply(messages, "term_a", "orphan");
+        var before = messages.drainReplies("term_a");
+        assertEquals(1, before.size(), "one reply in the inbox");
+        String msgId = before.getFirst().msgId();
+
+        // Publish the same reply again and ack it via bridge_ack surface.
+        BridgeMcp.reply(messages, "term_a", "orphan-again");
+        var peeked = messages.drainReplies("term_a");
+        assertEquals(1, peeked.size(), "one fresh reply in the inbox");
+
+        // ackReply works (no-op since published with a different UUID, but callable).
+        assertDoesNotThrow(() -> messages.ackReply("term_a", msgId));
+    }
+
     @Test
     void statusReportsLiveAgentStatus() {
         FakeHerdr blocked = new FakeHerdr().agentStatus("blocked");