feat(mosstank): add VTank-style automation PoC

tests/AcDream.Runtime.Tests/Gameplay/RuntimeActionStateTests.cs

@@ -7,6 +7,33 @@ namespace AcDream.Runtime.Tests.Gameplay;
 
 public sealed class RuntimeActionStateTests
 {
+    [Fact]
+    public void HealthActivityPublishesMonotonicRevisionAndAgeAndResets()
+    {
+        double now = 10d;
+        using var inventory = NewInventoryTransactions();
+        using var actions = RuntimeActionTestFactory.Create(inventory, () => now);
+
+        actions.Combat.OnUpdateHealth(0x50000001u, 0.75f);
+        now = 12.5d;
+
+        Assert.True(actions.TryGetHealthActivity(
+            0x50000001u, out long firstRevision, out double age));
+        Assert.Equal(1, firstRevision);
+        Assert.Equal(2.5d, age, 3);
+
+        actions.Combat.OnUpdateHealth(0x50000001u, 0.5f);
+        Assert.True(actions.TryGetHealthActivity(
+            0x50000001u, out long secondRevision, out age));
+        Assert.True(secondRevision > firstRevision);
+        Assert.Equal(0d, age, 3);
+
+        actions.ResetSession();
+        Assert.False(actions.TryGetHealthActivity(
+            0x50000001u, out _, out double missingAge));
+        Assert.True(double.IsPositiveInfinity(missingAge));
+    }
+
     [Fact]
     public void ViewProjectsTheExactCanonicalChildrenAndRevisions()
     {