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>

src/AcDream.App/Plugins/AppAutomationSurface.cs

@@ -1,3 +1,4 @@
+using AcDream.Core.Chat;
 using AcDream.Core.Player;
 using AcDream.Core.Spells;
 using AcDream.Plugin.Abstractions;
@@ -25,11 +26,13 @@ namespace AcDream.App.Plugins;
 /// </para>
 /// </remarks>
 internal sealed class AppAutomationSurface
-    : IAutomationSurface, ICharacterInfo, ISpellCatalog, IMagicCommands, IDisposable
+    : IAutomationSurface, ICharacterInfo, ISpellCatalog, IMagicCommands, IPluginChat,
+      IDisposable
 {
     private readonly object _gate = new();
 
     private GameRuntime? _runtime;
+    private RuntimeCommunicationState? _communication;
     private RuntimeCharacterState? _character;
     private RuntimeSpellCastState? _cast;
     private Spellbook? _spellbook;
@@ -74,6 +77,7 @@ internal sealed class AppAutomationSurface
     public ICharacterInfo Character => this;
     public ISpellCatalog Spells => this;
     public IMagicCommands Magic => this;
+    public IPluginChat Chat => this;
 
     /// <summary>Bind the surface to the runtime's gameplay owners.</summary>
     public void Bind(
@@ -90,6 +94,7 @@ internal sealed class AppAutomationSurface
                 return;
             DetachLocked();
             _runtime = runtime;
+            _communication = runtime.CommunicationOwner;
             _character = character;
             _cast = cast;
             _spellbook = spellbook;
@@ -132,6 +137,7 @@ internal sealed class AppAutomationSurface
         _character = null;
         _cast = null;
         _runtime = null;
+        _communication = null;
     }
 
     private void OnSpellbookChanged() => RebuildSpellbook();
@@ -361,6 +367,22 @@ internal sealed class AppAutomationSurface
         return false;
     }
 
+    // ── IPluginChat ───────────────────────────────────────────────────────
+    /// <summary>
+    /// Routed to retail's ClientLocal log type (0x1A) — the channel the client
+    /// uses for its own notices. Nothing reaches the server, so a plugin cannot
+    /// accidentally speak in the player's name.
+    /// </summary>
+    public void PostSystemMessage(string text)
+    {
+        if (string.IsNullOrEmpty(text))
+            return;
+        RuntimeCommunicationState? communication;
+        lock (_gate)
+            communication = _communication;
+        communication?.AddText(text, RetailLogTextType.ClientLocal);
+    }
+
     // ── IMagicCommands ────────────────────────────────────────────────────
     public bool IsCasting
     {