feat(chat): the talk-focus menu's Tell-to / Squelch entries actually work

Both entries were deliberate no-ops — the code said so — and both showed a
static label where retail shows the selected player's NAME.

Retail builds them in gmMainChatUI::InitTalkFocusMenu @0x004CDC50 and rebuilds
their labels every time the menu opens, substituting the selection through
StringInfo::AddVariable_String (@0x004CD91C / @0x004CD982). So they now read
"Tell to Dww" / "Squelch (ignore) Dww", rebuilt on open from a live selection
provider, and grey out with nothing selected — retail arms the tell slot only
for a talkable target (SetTalkFocusEnabled(2, 1) @0x004CD9B0).

Picking "Tell to X" aims the chat bar at X. That needed one piece of plumbing:
the parser's plain-speech fallthrough returned a null target, so a line typed
under a Tell focus was dropped by the router for having no one to send to.
Parse/Submit now carry an optional default tell target for exactly that case.

"Squelch X" publishes the ALREADY-REGISTERED /squelch verb rather than
reimplementing the request — the ModifyCharacterSquelch wire builder
(CM_Communication::Event_ModifyCharacterSquelch @0x006A42D0) has been there all
along; only the menu path to it was missing.

UiMenu gains an OnOpen seam, because a menu whose Items are fixed at Bind can
only ever say "Tell to Selected". It fires before _open flips so the rebuilt
rows are measured and drawn in the same opening.

Solution builds clean; 14,480 tests pass on the standard hermetic lane filter,
0 failures.

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

src/AcDream.App/UI/UiMenu.cs

@@ -28,6 +28,17 @@ public sealed class UiMenu : UiElement
     /// <summary>Fired with the picked item's payload when a row is chosen.</summary>
     public Action<object?>? OnSelect { get; set; }
 
+    /// <summary>
+    /// Raised as the popup opens, before the rows are measured or drawn.
+    /// </summary>
+    /// <remarks>
+    /// Retail rebuilds the talk-focus menu's two selection-dependent entries
+    /// each time it opens (gmMainChatUI @0x004CD8E9), so their labels track
+    /// whoever is selected right now. A menu whose Items were fixed at Bind
+    /// could only ever say "Tell to Selected".
+    /// </remarks>
+    public Action? OnOpen { get; set; }
+
     /// <summary>Per-payload enabled gate (disabled rows render greyed + are inert). Null ⇒ all enabled.</summary>
     public Func<object?, bool>? EnabledProvider { get; set; }
 
@@ -258,6 +269,9 @@ public sealed class UiMenu : UiElement
     private void SetOpen(bool value)
     {
         if (_open == value) return;
+        // Before _open flips, so a handler that replaces Items is reflected in
+        // the very first measure/draw of this opening.
+        if (value) OnOpen?.Invoke();
         _open = value;
         if (FindRoot() is not { } root) return;
         if (value) root.SetActivePopup(this, () => SetOpen(false));