Merge nucleic/lucid-river-toad-6efj into dev

NucleicBroker.Tests/BrokerServiceTests.cs

@@ -112,6 +112,23 @@ public sealed class BrokerServiceTests
         Assert.Equal(new SessionSpec("nucleic-dev", @"C:\data", 4, 8192), wslc.LastSession);
     }
 
+    /// <summary>
+    /// D13 Tier 1 (docs/WINDOWS_PORT.md §13.2): the facade auto-recovers a session orphaned by a
+    /// dead broker, but when the internal COM arm did not bind there is nothing it can do — and
+    /// hostd must be able to tell *that* apart from an ordinary start failure, because the remedy
+    /// is `wsl --shutdown` rather than a retry. This pins the kind the Swift side branches on.
+    /// </summary>
+    [Fact]
+    public async Task SessionEnsure_UnrecoverableConflict_SurfacesSessionExists()
+    {
+        wslc.NextError = new WslcError(WslcError.SessionExists, "already running, cannot re-adopt");
+        var lines = await RoundTrip(
+            """{"jsonrpc":"2.0","id":9,"method":"session.ensure","params":{"name":"nucleic-dev","dataDir":"C:\\data"}}""");
+        var error = Assert.Single(lines).GetProperty("error");
+        Assert.Equal(Rpc.FacadeError, error.GetProperty("code").GetInt32());
+        Assert.Equal("session_exists", error.GetProperty("data").GetProperty("kind").GetString());
+    }
+
     [Fact]
     public async Task ImagePull_EmitsProgressNotificationsBeforeResult()
     {