Event-driven dialog queue, story flag command, mod unit tests

Push-based event chains, runtime fixes (single end, goto lifecycle, if,
busy box, held delay, empty options, timed/animated/effect actions), the
'flag name value' DSL command, autoplay --dialogs=N, 19 mod unit tests.

tests/HoldDebugger.cs

@@ -0,0 +1,25 @@
+namespace Cthangover.Mods.Dialog.Tests
+{
+    using Cthangover.Mods.Dialog.Action;
+
+    /// <summary>
+    /// Debugger stand-in that holds the runtime once, right before
+    /// <see cref="Target"/> — what the scenario studio does on a breakpoint.
+    /// </summary>
+    public class HoldDebugger : IDialogDebugger
+    {
+        private bool held;
+
+        /// <summary>The action to hold before.</summary>
+        public IActionCommand Target { get; set; }
+
+        /// <summary>Holds before <see cref="Target"/> the first time it is reached.</summary>
+        public bool ShouldHold(DialogRuntime runtime, IActionCommand action)
+        {
+            if (held || action != Target)
+                return false;
+            held = true;
+            return true;
+        }
+    }
+}