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.Plugins.MossTank/MossTankPanel.cs

@@ -94,6 +94,7 @@ internal sealed class MossTankPanel
         if (_running)
         {
             Stop("Stopped.");
+            Announce("Stopped.");
             return;
         }
 
@@ -114,6 +115,18 @@ internal sealed class MossTankPanel
             ? "Checking…"
             : $"Buffing 0/{_plan.Count}…";
         _host.Log.Info($"MossTank: pass started, {_plan.Count} buff(s) queued");
+        Announce(_plan.Count == 0
+            ? "Buffing — checking what needs recasting."
+            : $"Buffing — {_plan.Count} spell(s) to cast.");
+    }
+
+    /// <summary>
+    /// One chat line, tagged so it reads like a client notice rather than
+    /// something the character said.
+    /// </summary>
+    private void Announce(string text)
+    {
+        _host.Automation.Chat.PostSystemMessage($"[MossTank] {text}");
     }
 
     private void Stop(string status)
@@ -163,6 +176,7 @@ internal sealed class MossTankPanel
         {
             Stop($"Stalled after {_castThisPass} cast(s).");
             _host.Log.Warn("MossTank: pass stalled; stopping");
+            Announce($"Stopped — no progress after {_castThisPass} cast(s).");
             return;
         }
 
@@ -182,6 +196,9 @@ internal sealed class MossTankPanel
         {
             Stop($"Done — {_castThisPass} cast(s).");
             _host.Log.Info($"MossTank: pass complete ({_castThisPass} cast)");
+            Announce(_castThisPass == 0
+                ? "Already fully buffed."
+                : $"Finished — {_castThisPass} spell(s) cast.");
             return;
         }