fix(vt): list column fix round 9/11 — MossTankMarkupContractTests learns <column>

The contract test suite's per-element binding-shape check treated
EVERY element's onclick as a plain Action, and its interactive-element
set (used both for "declares a real handler" and "has an accessible
tooltip") had no entry for <column> at all — both would misvalidate a
future mosstank.xml <column> the way Campaign VT slice 1 Part B and
this fix round's item 1 actually shipped it (onchange/onclick as
Action<int>, the row index).

Extracted the per-element dispatch out of
EveryInteractiveBindingMatchesTheRetainedUiDelegateShape into
AssertElementBindingsMatchRetainedUiDelegateShape, which now
special-cases "column": both onchange and onclick must resolve to
Action<int>, never plain Action. The interactive-element name list is
now the single shared InteractiveElementNames array (was duplicated
inline in EveryInteractiveControlDeclaresARealHandlerBinding and
TextlessAndAbbreviatedControlsHaveAccessibleRetailTooltips), with
"column" added — zero behavior change against mosstank.xml today (it
has no <column> elements yet), confirmed by the existing 190-control
count assertion staying green.

New tests: InteractiveElementNames_IncludesColumn pins the addition
directly; Column_OnchangeAndOnclick_MustBeActionOfInt builds a
synthetic <column> (not loaded from mosstank.xml, which has none) and
proves both a correctly-typed Action<int> onchange passes and a
column onclick bound to a plain Action (the shape every OTHER
element's onclick uses) is rejected — confirmed by temporarily
removing the "column" special case and rerunning: the plain-Action
onclick then passed silently ("No exception was thrown", the
generic Action check being satisfied by a real Action property),
proving the test only passes because the fix's column-specific
Action<int> enforcement is present.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tests/AcDream.Plugins.MossTank.Tests/MossTankMarkupContractTests.cs

@@ -6,6 +6,29 @@ namespace AcDream.Plugins.MossTank.Tests;
 
 public sealed class MossTankMarkupContractTests
 {
+    /// <summary>
+    /// Fix round item 9: every element name whose interactive attributes
+    /// (onclick/onchange/onsubmit) this contract validates and requires a
+    /// real handler for — shared by
+    /// <see cref="EveryInteractiveControlDeclaresARealHandlerBinding"/> and
+    /// <see cref="TextlessAndAbbreviatedControlsHaveAccessibleRetailTooltips"/>.
+    /// <c>column</c> (Campaign VT slice 1 Part B's <c>&lt;list&gt;&lt;column&gt;</c>)
+    /// joined this set here — mosstank.xml itself has no <c>&lt;column&gt;</c>
+    /// elements yet, so this is a zero-behavior-change addition against the
+    /// current file (see <see cref="InteractiveElementNames_IncludesColumn"/>
+    /// for the direct pin).
+    /// </summary>
+    private static readonly string[] InteractiveElementNames =
+    [
+        "tab", "button", "toggle", "slider", "field", "menu", "list", "column",
+    ];
+
+    [Fact]
+    public void InteractiveElementNames_IncludesColumn()
+    {
+        Assert.Contains("column", InteractiveElementNames);
+    }
+
     [Fact]
     public void VtankTabOrderAndEveryBindingResolveAgainstTheLivePanel()
     {
@@ -54,24 +77,80 @@ public sealed class MossTankMarkupContractTests
             StringComparer.Ordinal);
 
         foreach (XElement element in root.DescendantsAndSelf())
-        {
+            AssertElementBindingsMatchRetainedUiDelegateShape(element, byName);
-            AssertBindingType(element, "onclick", typeof(Action), byName);
+    }
-            AssertBindingType(
-                element,
-                "onsubmit",
-                typeof(Action<string>),
-                byName);
 
-            Type? changeType = element.Name.LocalName switch
+    /// <summary>
-            {
+    /// Fix round item 9: <c>&lt;column&gt;</c>'s own <c>onchange</c> (a
-                "field" or "menu" => typeof(Action<string>),
+    /// <c>type="check"</c> column) and <c>onclick</c> (<c>type="icon"</c>,
-                "slider" => typeof(Action<float>),
+    /// or a <c>type="text"</c> column's fix-item-1 optional onclick) are
-                "list" => typeof(Action<int>),
+    /// BOTH <c>Action&lt;int&gt;</c> (the row index) — never the plain
-                _ => null,
+    /// <c>Action</c> every other element's <c>onclick</c> resolves to.
-            };
+    /// Extracted out of <see cref="EveryInteractiveBindingMatchesTheRetainedUiDelegateShape"/>
-            if (changeType is not null)
+    /// so <see cref="Column_OnchangeAndOnclick_MustBeActionOfInt"/> can drive
-                AssertBindingType(element, "onchange", changeType, byName);
+    /// it directly against a synthetic <c>&lt;column&gt;</c> element —
+    /// mosstank.xml itself has none yet.
+    /// </summary>
+    private static void AssertElementBindingsMatchRetainedUiDelegateShape(
+        XElement element,
+        IReadOnlyDictionary<string, PropertyInfo> byName)
+    {
+        if (element.Name.LocalName == "column")
+        {
+            AssertBindingType(element, "onchange", typeof(Action<int>), byName);
+            AssertBindingType(element, "onclick", typeof(Action<int>), byName);
+            return;
         }
+
+        AssertBindingType(element, "onclick", typeof(Action), byName);
+        AssertBindingType(
+            element,
+            "onsubmit",
+            typeof(Action<string>),
+            byName);
+
+        Type? changeType = element.Name.LocalName switch
+        {
+            "field" or "menu" => typeof(Action<string>),
+            "slider" => typeof(Action<float>),
+            "list" => typeof(Action<int>),
+            _ => null,
+        };
+        if (changeType is not null)
+            AssertBindingType(element, "onchange", changeType, byName);
+    }
+
+    private sealed class ColumnBindingProbe
+    {
+        public Action<int> RowAction { get; } = _ => { };
+        public Action PlainAction { get; } = () => { };
+    }
+
+    [Fact]
+    public void Column_OnchangeAndOnclick_MustBeActionOfInt()
+    {
+        var byName = typeof(ColumnBindingProbe)
+            .GetProperties(BindingFlags.Instance | BindingFlags.Public)
+            .ToDictionary(static property => property.Name, StringComparer.Ordinal);
+
+        // Correctly typed Action<int> — must not throw.
+        var goodColumn = new XElement(
+            "column",
+            new XAttribute("type", "check"),
+            new XAttribute("onchange", "{RowAction}"));
+        AssertElementBindingsMatchRetainedUiDelegateShape(goodColumn, byName);
+
+        // A column's onclick bound to a PLAIN Action (the shape every other
+        // element's onclick uses) must be rejected — proves the dispatch
+        // actually enforces Action<int> for <column> specifically, rather
+        // than silently accepting whatever the generic non-column path
+        // would have allowed.
+        var badColumn = new XElement(
+            "column",
+            new XAttribute("type", "icon"),
+            new XAttribute("onclick", "{PlainAction}"));
+        Assert.Throws<Xunit.Sdk.EqualException>(
+            () => AssertElementBindingsMatchRetainedUiDelegateShape(badColumn, byName));
     }
 
     [Fact]
@@ -80,10 +159,7 @@ public sealed class MossTankMarkupContractTests
         XDocument document = XDocument.Load(
             Path.Combine(AppContext.BaseDirectory, "mosstank.xml"));
         XElement root = Assert.IsType<XElement>(document.Root);
-        HashSet<string> interactive = new(
+        HashSet<string> interactive = new(InteractiveElementNames, StringComparer.Ordinal);
-        [
-            "tab", "button", "toggle", "slider", "field", "menu", "list",
-        ], StringComparer.Ordinal);
 
         XElement[] controls = root.Descendants()
             .Where(element => interactive.Contains(element.Name.LocalName))
@@ -134,10 +210,7 @@ public sealed class MossTankMarkupContractTests
         XDocument document = XDocument.Load(
             Path.Combine(AppContext.BaseDirectory, "mosstank.xml"));
         XElement root = Assert.IsType<XElement>(document.Root);
-        string[] interactive =
+        string[] interactive = InteractiveElementNames;
-        [
-            "tab", "button", "toggle", "slider", "field", "menu", "list",
-        ];
         HashSet<string> terse = new(
         [
             "+", "-", "↑", "↓", "F", "B", "G", "I", "Y", "V", "A",