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

NucleicBroker.Tests/BrokerServiceTests.cs

@@ -51,6 +51,31 @@ public sealed class BrokerServiceTests
         var caps = result.GetProperty("capabilities").EnumerateArray().Select(c => c.GetString()).ToList();
         Assert.Contains("proc", caps);
         Assert.DoesNotContain("ai", caps);  // UnavailableAiProvider
+        // The facade's own capabilities ride the same list as the RPC families, because hostd
+        // needs both to decide what to attempt (docs/WINDOWS_PORT.md D13).
+        Assert.Contains("tty", caps);
+        Assert.Contains("reattach", caps);
+    }
+
+    /// <summary>
+    /// A compat-SDK-only facade reports no `tty`/`reattach`/`enumerate`, and that MUST reach
+    /// hostd through `hello` — it is the whole degradation mechanism D13 relies on, and the
+    /// difference between the Terminal panel being disabled and it failing in the user's face.
+    /// </summary>
+    [Fact]
+    public async Task Hello_OmitsCapabilitiesTheFacadeCannotServe()
+    {
+        wslc.CapabilityList = ["stats"];   // what WslcFacade reports with only the compat SDK
+        var result = Result(Assert.Single(await RoundTrip("""{"jsonrpc":"2.0","id":1,"method":"hello"}""")));
+        var caps = result.GetProperty("capabilities").EnumerateArray().Select(c => c.GetString()).ToList();
+        Assert.Contains("stats", caps);
+        Assert.DoesNotContain("tty", caps);
+        Assert.DoesNotContain("reattach", caps);
+        Assert.DoesNotContain("enumerate", caps);
+        // The RPC families are still advertised: the methods exist and answer, they just answer
+        // `unsupported` for the parts the surface cannot do.
+        Assert.Contains("container", caps);
+        Assert.Contains("proc", caps);
     }
 
     [Fact]