fix(mosstank): unclickable button, empty skill list, dev font, and chat output

Four defects from the first in-world look, three of them with a definite root
cause rather than a plausible one.

**The Buff button did nothing.** Not a hit-testing problem -- the pointer found
the button perfectly. UiRoot's press handling asks the pressed widget whether
it owns the pointer; a widget that does not claim the press falls through to
"move the ancestor window", and a window drag returns early on release without
ever emitting a Click. UiButton and UiClickablePanel both override
HandlesClick for exactly this reason; UiSimpleButton never did. Latent since
that class was written, and invisible until it was put inside a draggable
window -- which is precisely what a markup plugin panel is.

Found by reproducing it headlessly through the real UiRoot dispatcher rather
than by reasoning about it: MarkupPanelClickTests drives press-and-release over
the button and asserts the bound action ran, with a separate test asserting the
pointer finds the button at all, so a future failure says which half broke.
My earlier guess -- that a modal at character select was swallowing the click
-- was wrong, and the screenshot of the panel live in world disproved it.

**"0 trained skills".** The skill-name table was read in OnLoad *before*
GameWindowCompositionPipeline.Run, which is what publishes the DAT collection,
so _dats was still null, the whole block was skipped, and the surface reported
an empty skill list with nothing to explain it. Bound in PublishDatCollection
instead -- the moment the data exists -- so it cannot run early again whatever
the phase ordering does, and a genuinely missing SkillTable now says so.

**Plugin text used the development bitmap font.** UiLabel and UiSimpleButton
gained a DatFont, and MarkupDocument now takes the retail interface font from
the host, so plugin panels render through the same glyph path (including
retail's two-plane outline) as authored panels.

**MossTank now writes to chat.** New BCL-only IPluginChat routes to retail's
ClientLocal log type (0x1A) -- the channel the client uses for its own notices,
local to this client, so a plugin cannot speak in the player's name. MossTank
announces the start, the finish with a cast count, and a stall.

Not addressed here: the cursor showing blue rather than amber. Traced but not
fixed -- CursorFeedbackController picks the cursor family from combat mode, and
CombatMode.Magic selects the blue Magic cursor where Default is amber. That is
a combat-mode question, unrelated to this change, and worth its own look rather
than a speculative fix folded in here.

Solution builds clean; 14,437 tests pass on the standard hermetic lane filter,
0 failures.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/AcDream.App.Tests/UI/MarkupPanelClickTests.cs

@@ -0,0 +1,97 @@
+using AcDream.App.UI;
+using Xunit;
+
+namespace AcDream.App.Tests.UI;
+
+/// <summary>
+/// End-to-end click routing for a markup-built plugin panel: press and release
+/// over the button, through the real <see cref="UiRoot"/> dispatcher, and
+/// assert the bound action ran.
+/// </summary>
+/// <remarks>
+/// Written because a MossTank panel rendered correctly in world and its Buff
+/// button did nothing when clicked. Unit-testing the markup builder proved the
+/// handler was bound; only driving the actual pointer path can show whether the
+/// click reaches it.
+/// </remarks>
+public class MarkupPanelClickTests
+{
+    private sealed class Binding
+    {
+        public int Clicks { get; private set; }
+        public Action Go => () => Clicks++;
+        public bool Shown { get; set; } = true;
+        public string Status => "ok";
+    }
+
+    private const string Markup =
+        "<panel x=\"40\" y=\"120\" w=\"360\" h=\"132\" title=\"MossTank\" visible=\"{Shown}\">"
+        + "  <label x=\"12\" y=\"30\" text=\"{Status}\"/>"
+        + "  <button x=\"12\" y=\"94\" w=\"108\" h=\"28\" text=\"Buff\" onclick=\"{Go}\"/>"
+        + "</panel>";
+
+    private static (UiRoot Root, Binding Bound) Mount()
+    {
+        var bound = new Binding();
+        UiNineSlicePanel panel =
+            MarkupDocument.Build(Markup, bound, _ => ((uint)1, 32, 32));
+        var root = new UiRoot { Width = 1280, Height = 720 };
+        root.AddChild(panel);
+        return (root, bound);
+    }
+
+    /// <summary>Centre of the button in root space: panel(40,120) + button(12,94) + half.</summary>
+    private static (int X, int Y) ButtonCentre() => (40 + 12 + 54, 120 + 94 + 14);
+
+    [Fact]
+    public void ClickingTheButtonRunsTheBoundAction()
+    {
+        var (root, bound) = Mount();
+        (int x, int y) = ButtonCentre();
+
+        root.OnMouseDown(UiMouseButton.Left, x, y);
+        root.OnMouseUp(UiMouseButton.Left, x, y);
+
+        Assert.Equal(1, bound.Clicks);
+    }
+
+    [Fact]
+    public void ThePointerFindsTheButtonAtAll()
+    {
+        // Separated from the click test so a failure says whether the problem is
+        // hit-testing or event dispatch.
+        var (root, _) = Mount();
+        (int x, int y) = ButtonCentre();
+
+        UiElement? hit = root.Pick(x, y);
+
+        Assert.NotNull(hit);
+        Assert.IsType<UiSimpleButton>(hit);
+    }
+
+    [Fact]
+    public void ClickingOutsideTheButtonDoesNotRunTheAction()
+    {
+        var (root, bound) = Mount();
+
+        root.OnMouseDown(UiMouseButton.Left, 900, 600);
+        root.OnMouseUp(UiMouseButton.Left, 900, 600);
+
+        Assert.Equal(0, bound.Clicks);
+    }
+
+    [Fact]
+    public void AHiddenPanelSwallowsNothing()
+    {
+        var (root, bound) = Mount();
+        bound.Shown = false;
+        root.Tick(0.016, 0);            // visibility source is evaluated on tick
+        (int x, int y) = ButtonCentre();
+
+        root.OnMouseDown(UiMouseButton.Left, x, y);
+        root.OnMouseUp(UiMouseButton.Left, x, y);
+
+        Assert.Equal(0, bound.Clicks);
+        Assert.Null(root.Pick(x, y));
+    }
+}