feat(ui): FA3 -- mount the social panel shell (Friends/Allegiance/Fellowship/Squelch)

Campaign FA slice FA3: retail's four-tab social panel (LayoutDesc
0x2100006E slot 0x1000018F, RetailPanelCatalog id 12), built on the OP3
OptionsPanelController recipe -- Type-8 tab host, ActivateTabBehavior,
per-page scoped controllers.

- SocialPanelController mounts the tab host and wires the close button;
  F3 (ToggleAllegiancePanel) and F4 (ToggleFellowshipPanel) open the
  panel and switch to their own tab, sharing the same gmPanelUI
  one-active-panel exclusivity every sibling main panel already has.
- The live-DAT tab table CORRECTS the coordinator addendum's x-order
  guess: button 0x1000028C ("Allegiance") pairs with page 0x10000291 and
  is the authored DEFAULT entry, not Friends -- each button's own page
  id and its own P0x57 (matching the F3/F4 ActionMap ids on the
  Allegiance/Fellowship pages specifically) both corroborate the real
  pairing. See SocialPanelController's class doc for the full table.
- SocialFellowshipPageController swaps the two authored empty/full
  frames (0x1000026B/0x10000275) on RuntimeFellowshipState's
  IsInFellowship -- both frames' full containment (name box, create
  button, checkboxes vs. roster list, six buttons) was confirmed by the
  live-mount probe, so a single Visible toggle per frame is the whole
  swap (closes lane-A unknown U6).
- SocialAllegiancePageController hides the monarch/patron blocks and
  blanks their name text to a literal space when
  RuntimeAllegianceState.Snapshot.HasProfile is false, using SCOPED
  FindDescendant lookups (the panel authors 0x10000492 twice, once per
  block).
- SocialFriendsPageController/SocialSquelchPageController bind their
  ListBoxes read-only to RuntimeCommunicationState's existing J4.1
  Friends/Squelch owners (names only), rebuilding on revision change.
  Their action buttons are honest INERT (D1) -- register row AD-79.
- UiTemplateListBox gains Flush() (lane A/D's "Gap found" prerequisite)
  so a poll-and-rebuild list can shrink between refreshes.
- RetailPanelCatalog.SocialPanel = 12, byte-verified from the live slot's
  own P0x10000029; listed in Mounted only (no toolbar button -- lane A
  §6.1: the open path is keyboard-only).

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

src/AcDream.App/UI/Layout/SocialAllegiancePageController.cs

@@ -0,0 +1,112 @@
+using System;
+using System.Collections.Generic;
+using AcDream.Runtime;
+
+namespace AcDream.App.UI.Layout;
+
+/// <summary>
+/// Campaign FA slice FA3: the Allegiance page's empty-state presentation —
+/// the ONLY behavior this SHELL slice owns for this page (live monarch/
+/// patron/vassal population, swear/break/kick + confirmations, and the
+/// per-member online-state dimming are FA5 scope).
+///
+/// <para>
+/// Retail has no frame swap for Allegiance (unlike Fellowship) — instead it
+/// hides the monarch/patron blocks and blanks their name text to a literal
+/// space per-block, gated on whether each relationship exists
+/// (docs/research/2026-08-11-fa-panel-structure.md §4.5). FA3's contract
+/// simplifies this to the single gate this campaign's Runtime owner
+/// actually exposes today: <see cref="RuntimeAllegianceSnapshot.HasProfile"/>
+/// — no allegiance push has landed this generation. When a profile HAS
+/// arrived, this controller leaves both blocks visible with their
+/// build-time (empty) text rather than fabricate monarch/patron content —
+/// that population is FA5's job.
+/// </para>
+///
+/// <para>
+/// Element ids confirmed by the FA3 live-mount probe:
+/// <c>0x10000255</c> monarch-field container, <c>0x1000025A</c>
+/// patron-field container, <c>0x10000257</c> monarch-name text (inside the
+/// monarch field), <c>0x1000025C</c> patron-name text (inside the patron
+/// field). Both lookups are SCOPED to the allegiance page root — the panel
+/// also authors <c>0x10000492</c> (the XP-passed-up text) TWICE, once under
+/// each block, so a flat lookup anywhere in this subsystem would risk
+/// picking the wrong instance (§6 DISCIPLINE, the campaign-OP
+/// <c>0x10000211</c>-in-two-layouts lesson).
+/// </para>
+/// </summary>
+public sealed class SocialAllegiancePageController
+{
+    private static readonly IReadOnlyList<UiText.Line> BlankLine =
+        [new UiText.Line(" ", System.Numerics.Vector4.One)];
+
+    private static readonly IReadOnlyList<UiText.Line> NoLines = [];
+
+    private readonly UiElement _monarchField;
+    private readonly UiElement _patronField;
+    private readonly UiText? _monarchName;
+    private readonly UiText? _patronName;
+    private readonly Func<RuntimeAllegianceSnapshot> _snapshot;
+
+    private SocialAllegiancePageController(
+        UiElement monarchField,
+        UiElement patronField,
+        UiText? monarchName,
+        UiText? patronName,
+        Func<RuntimeAllegianceSnapshot> snapshot)
+    {
+        _monarchField = monarchField;
+        _patronField = patronField;
+        _monarchName = monarchName;
+        _patronName = patronName;
+        _snapshot = snapshot;
+    }
+
+    public static SocialAllegiancePageController? Bind(
+        UiElement pageRoot,
+        Func<RuntimeAllegianceSnapshot> snapshot)
+    {
+        ArgumentNullException.ThrowIfNull(pageRoot);
+        ArgumentNullException.ThrowIfNull(snapshot);
+
+        if (UiElement.FindDescendant(pageRoot, 0x10000255u) is not { } monarchField
+            || UiElement.FindDescendant(pageRoot, 0x1000025Au) is not { } patronField)
+        {
+            Console.WriteLine(
+                "[D.2b] SocialAllegiancePageController: monarch/patron field "
+                + "containers (0x10000255/0x1000025A) not found — allegiance page "
+                + "will not present its empty state.");
+            return null;
+        }
+
+        // Scoped to each block — 0x10000257/0x1000025C are unique per-block,
+        // but the lookup discipline matters equally here (see class doc).
+        UiText? monarchName = UiElement.FindDescendant(monarchField, 0x10000257u) as UiText;
+        UiText? patronName = UiElement.FindDescendant(patronField, 0x1000025Cu) as UiText;
+        if (monarchName is null)
+            Console.WriteLine("[D.2b] SocialAllegiancePageController: monarch name text 0x10000257 not found.");
+        if (patronName is null)
+            Console.WriteLine("[D.2b] SocialAllegiancePageController: patron name text 0x1000025C not found.");
+
+        var controller = new SocialAllegiancePageController(
+            monarchField, patronField, monarchName, patronName, snapshot);
+        controller.Tick();
+        return controller;
+    }
+
+    /// <summary>
+    /// Re-reads the live snapshot and applies the FA3 empty-state gate. Cheap
+    /// — called every frame from <see cref="SocialPanelController.Tick"/> (same
+    /// reasoning as <see cref="SocialFellowshipPageController.Tick"/>).
+    /// </summary>
+    public void Tick()
+    {
+        bool hasProfile = _snapshot().HasProfile;
+        _monarchField.Visible = hasProfile;
+        _patronField.Visible = hasProfile;
+
+        IReadOnlyList<UiText.Line> lines = hasProfile ? NoLines : BlankLine;
+        if (_monarchName is not null) _monarchName.LinesProvider = () => lines;
+        if (_patronName is not null) _patronName.LinesProvider = () => lines;
+    }
+}