feat(runtime): FA2 -- RuntimeFellowshipState + RuntimeAllegianceState sibling J-owners

Two new sibling Runtime owners under GameRuntime per the Slice-J
pattern (D2): RuntimeFellowshipState is session-scoped (a new
RuntimeGenerationResetStage.Fellowship clears it at every generation
reset, matching the ExternalContainer precedent); RuntimeAllegianceState
survives reconnect behind a HasServerSeed-style one-way latch and
participates in NO reset stage (its data persists like a real
disconnect does not sever allegiance membership).

Fellowship: full-update REPLACE, incremental-fellow UPSERT, self-vs-
other quit/dismiss removal (self clears the whole snapshot), disband
clear, and retail's leader hand-off rule for the Quit button
(RequiresLeaderHandoffBeforeQuit -- the current leader quitting WITHOUT
disbanding must send 0x0290 AssignNewLeader before 0x00A3, lane B
§2.5/§3.6).

Allegiance: seeded by AllegianceUpdate (0x0020, always self) and,
self-gated on TargetGuid == playerGuid(), by AllegianceInfoResponse
(0x027C); wraps the FA1-assembled flat AllegianceMemberRecord list
directly (AllegianceTree was deleted at FA1 -- nothing left to wrap).

Both apply the full 8-edit J-owner template: construction + fault
points + Owner/View properties + CaptureOwnership + a new
GameRuntimeTeardownStage pair (FellowshipDisposed/AllegianceDisposed,
stage count 11->13) + RuntimeGameplayOwnershipSnapshot inclusion +
RuntimeStateCheckpoint/trace fields. IRuntimeFellowshipCommands/
IRuntimeAllegianceCommands added to IGameRuntimeCommands and
implemented on DirectGameRuntimeCommandAdapter. No IRuntimeEventObserver
member added (D2) -- consumers poll Snapshot.Revision.

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

src/AcDream.Runtime/Session/LiveSessionEventRouter.cs

@@ -79,7 +79,13 @@ public sealed record LiveSocialSessionBindings(
     // existing caller (including tests that build a bare ChatLog with no
     // owning RuntimeCommunicationState) compiles unchanged; GameEventWiring
     // falls back to its pre-CH2 chat-only behavior when this is null.
-    Action<string, RetailLogTextType>? AddText = null);
+    Action<string, RetailLogTextType>? AddText = null,
+    // Campaign FA slice FA2 (2026-08-12): the two sibling J-owners.
+    // Trailing/optional so every existing positional caller (Headless)
+    // compiles unchanged (docs/research/2026-08-11-fa-acdream-seams.md
+    // §2.4 — "the established compatibility convention").
+    RuntimeFellowshipState? Fellowship = null,
+    RuntimeAllegianceState? Allegiance = null);
 
 /// <summary>
 /// Owns every inbound subscription for one exact live session. Domain state
@@ -228,7 +234,34 @@ public sealed class LiveSessionEventRouter : ILiveSessionEventRouting
                 externalContainers: inventory.ExternalContainers,
                 vendor: inventory.Vendor,
                 onInterfaceText: social.AddText,
-                accepting: IsAccepting));
+                accepting: IsAccepting,
+                // Campaign FA slice FA2 (2026-08-12): fellowship/allegiance
+                // sink registration — the ONE inbound registration site
+                // (docs/research/2026-08-11-fa-acdream-seams.md §2.1),
+                // reached identically by both hosts since LiveSessionEventRouter
+                // itself is shared (LiveSessionEventRouter.Attach, K-slice
+                // unification).
+                onFellowshipFullUpdate: update =>
+                    social.Fellowship?.ApplyFullUpdate(update),
+                onFellowshipUpdateFellow: update =>
+                    social.Fellowship?.ApplyUpdateFellow(update),
+                onFellowshipQuit: quitterGuid =>
+                    social.Fellowship?.ApplyQuit(quitterGuid, inventory.PlayerGuid()),
+                onFellowshipDismiss: dismissedGuid =>
+                    social.Fellowship?.ApplyDismiss(dismissedGuid, inventory.PlayerGuid()),
+                onFellowshipDisband: () => social.Fellowship?.ApplyDisband(),
+                onAllegianceUpdate: update =>
+                    social.Allegiance?.ApplyUpdate(update),
+                onAllegianceInfoResponseSelf: response =>
+                    social.Allegiance?.ApplyInfoResponseSelf(response),
+                onAllegianceUpdateDone: weenieError =>
+                    social.Allegiance?.ApplyUpdateDone(weenieError),
+                onAllegianceUpdateAborted: weenieError =>
+                    social.Allegiance?.ApplyUpdateAborted(weenieError),
+                onAllegianceLoginNotification: notice =>
+                    social.Allegiance?.ApplyLoginNotification(
+                        notice.CharacterGuid,
+                        notice.IsLoggedIn)));
             ConstructionCheckpoint();
 
             // Campaign P Slice P1 (2026-07-30): burden recompute triggers —