fix #FA4-mechanism-MUST-FIX-3,SF-4: re-arm 0x00A6 on reconnect; unsubscribe ActivePageChanged on Dispose

MUST-FIX 3 -- SocialFellowshipPageController.SetPageVisible is edge-triggered
on a bool that survives a generation reset unchanged while the panel stays
open, so a reconnect never re-sends 0x00A6 and fellow vitals freeze for the
rest of the new session. SocialPanelController.ResetSessionDeclaration
clears the fellowship page's latch (SocialFellowshipPageController.
ResetPageVisibleLatch, this commit's counterpart) and re-evaluates the
existing "window shown AND Fellowship active" conjunction, wired into
RetailUiRuntime.ResetSessionTransientUi -- a seam that already runs on
every generation reset. A still-open Fellowship page re-declares; a closed
or other-tab page correctly stays silent.

SF-4 -- SocialPanelController's constructor subscribed an anonymous lambda
to UiTabPanel.ActivePageChanged with no way to remove it; Dispose only set
a flag. A tab switch after Dispose still reached
UpdateFellowshipPageVisibility and issued a Runtime command, since Tick's
own _disposed guard doesn't cover this event path. Stored the handler as a
field and unsubscribe it in Dispose.

Also adds the panel-level D4 conjunction test mechanism SF-5 flagged as
missing (the only prior D4 test exercised the PAGE controller's own
edge-trigger directly, never SocialPanelController's "window shown AND
Fellowship active" logic or its ActivePageChanged subscription).

Per docs/research/2026-08-12-fa4-review-mechanism.md.

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

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

@@ -105,6 +105,16 @@ public sealed class SocialPanelController : IRetainedPanelController
     private readonly SocialAllegiancePageController? _allegiance;
     private readonly SocialFriendsPageController? _friends;
     private readonly SocialSquelchPageController? _squelch;
+
+    /// <summary>Fix-round SF-4: stored so <see cref="Dispose"/> can
+    /// unsubscribe it — the constructor previously subscribed an anonymous
+    /// lambda with no way to remove it, so a tab switch reaching
+    /// <see cref="UiTabPanel.ActivePageChanged"/> AFTER <see cref="Dispose"/>
+    /// still dispatched into <see cref="UpdateFellowshipPageVisibility"/> and
+    /// a Runtime command (<c>Tick</c> itself already guards on
+    /// <see cref="_disposed"/>; this event does not go through <c>Tick</c>).</summary>
+    private readonly Action<uint, uint> _onActivePageChanged;
+
     private bool _disposed;
 
     /// <summary>Root element of the imported panel (the tab host itself —
@@ -136,8 +146,10 @@ public sealed class SocialPanelController : IRetainedPanelController
         // four-page mount that's the conjunction of both. Subscribed here
         // (not in Bind) so it observes every tab switch, including the
         // very first one ActivateTabBehavior's default-entry activation
-        // fires.
-        _tabPanel.ActivePageChanged += (_, _) => UpdateFellowshipPageVisibility();
+        // fires. Fix-round SF-4: stored as a field (not an inline lambda)
+        // so Dispose can unsubscribe it.
+        _onActivePageChanged = (_, _) => UpdateFellowshipPageVisibility();
+        _tabPanel.ActivePageChanged += _onActivePageChanged;
     }
 
     /// <summary>
@@ -267,6 +279,28 @@ public sealed class SocialPanelController : IRetainedPanelController
     private void UpdateFellowshipPageVisibility() =>
         _fellowship?.SetPageVisible(_visible && IsShowingFellowship);
 
+    /// <summary>
+    /// MUST-FIX 3 (FA4 fix round, 2026-08-12): called from
+    /// <see cref="RetailUiRuntime.ResetSessionTransientUi"/> — a seam that
+    /// already runs on every generation reset — to re-arm the Fellowship
+    /// page's <c>0x00A6</c> edge-trigger latch. <see cref="SocialPanelController"/>
+    /// is process-lifetime and the latch
+    /// (<see cref="SocialFellowshipPageController.SetPageVisible"/>) is
+    /// edge-triggered on a bool that survives a reconnect unchanged, so
+    /// without this a still-open Fellowship page never re-declares
+    /// <c>0x00A6</c> on the fresh session and every fellow's vitals freeze
+    /// for its remaining lifetime. Clears the latch, then re-evaluates the
+    /// SAME D4 conjunction <see cref="OnShown"/>/<see cref="OnHidden"/>/tab
+    /// switches use — a still-open Fellowship page re-declares; a closed or
+    /// other-tab page correctly stays silent (the conjunction is false, so
+    /// the now-cleared latch is simply left at its default).
+    /// </summary>
+    public void ResetSessionDeclaration()
+    {
+        _fellowship?.ResetPageVisibleLatch();
+        UpdateFellowshipPageVisibility();
+    }
+
     /// <summary>
     /// Per-frame poll: the Fellowship/Allegiance empty-state gates (no
     /// data-driven <see cref="UiElement.Visible"/> provider exists) and the
@@ -306,5 +340,9 @@ public sealed class SocialPanelController : IRetainedPanelController
     {
         if (_disposed) return;
         _disposed = true;
+        // Fix-round SF-4: without this, a tab switch after Dispose still
+        // reaches UpdateFellowshipPageVisibility -> a Runtime command —
+        // Tick's own _disposed guard doesn't cover this event handler.
+        _tabPanel.ActivePageChanged -= _onActivePageChanged;
     }
 }

src/AcDream.App/UI/RetailUiRuntime.cs

@@ -729,11 +729,24 @@ public sealed class RetailUiRuntime : IDisposable
         }
     }
 
+    /// <summary>
+    /// MUST-FIX 3 (FA4 fix round): also re-arms the fellowship page's
+    /// <c>0x00A6</c> panel-open declaration latch
+    /// (<see cref="Layout.SocialPanelController.ResetSessionDeclaration"/>).
+    /// <see cref="SocialPanelController"/> is process-lifetime, but its
+    /// edge-trigger latch is not — without this, a reconnect while the
+    /// Fellowship page is left open never re-sends <c>0x00A6</c> on the new
+    /// session, and every fellow's vitals freeze for the rest of the
+    /// session (lane B §4.5: ACE streams <c>0x02C0</c> only to fellows with
+    /// <c>FellowshipPanelOpen</c> set, and that flag is set only by
+    /// <c>0x00A6</c>).
+    /// </summary>
     public void ResetSessionTransientUi()
     {
         ResetSessionDialogs();
         AppraisalController?.ResetSession();
         Host.HideWindow(WindowNames.Examination);
+        SocialPanelController?.ResetSessionDeclaration();
     }
 
     public void UpdateCursor(IEnumerable<IMouse> mice)