refactor(app): complete session startup composition

Move the live-session reset and routing graph, combat and diagnostic command targets, and the sole gameplay input subscriber into Phase 7 before frame publication. Add exact retryable ownership for late bindings so partial startup cannot strand session or component teardown edges.

Co-authored-by: Codex <codex@openai.com>

tests/AcDream.App.Tests/Composition/InteractionUiRuntimeSourcesTests.cs

@@ -15,6 +15,23 @@ namespace AcDream.App.Tests.Composition;
 
 public sealed class InteractionUiRuntimeSourcesTests
 {
+    [Fact]
+    public void DesiredComponentSnapshotNormalizesNullAndClearsExactly()
+    {
+        var state = new DesiredComponentSnapshotState();
+        IReadOnlyList<(uint Id, uint Amount)> items =
+            [(0x01020304u, 7u)];
+
+        Assert.Empty(state.Items);
+        state.Items = items;
+        Assert.Same(items, state.Items);
+
+        state.Clear();
+        Assert.Empty(state.Items);
+        state.Items = null!;
+        Assert.Empty(state.Items);
+    }
+
     [Fact]
     public void SessionAuthorityDefaultsBindUnbindRebindAndDeactivateExactly()
     {