fix(runtime): restore interaction completion ownership

Preserve prepublication local motion completion, require the PartArray enter-world lifecycle port, and balance deferred Use busy ownership across dispatch and cancellation. Reconcile the completed GameWindow connected gates and add regression coverage.

Co-authored-by: Codex <codex@openai.com>

docs/research/2026-07-23-retail-use-busy-ownership-pseudocode.md

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+# Retail Use busy-reference ownership
+
+Date: 2026-07-23
+
+Scope: the retained UI busy cursor and the
+`You can only move or use one item at a time` gate while an object/NPC Use
+crosses acdream's close-range turn/approach boundary.
+
+## Retail oracle
+
+Named Sept-2013 retail symbols:
+
+- `ItemHolder::UseObject @ 0x00588A80`
+- `ClientUISystem::Handle_Item__UseDone @ 0x00564900`
+- `CM_Item::DispatchUI_UseDone @ 0x006A8510`
+- `ClientUISystem::UsageCallback @ 0x00565B20`
+
+`ItemHolder::UseObject` checks the 200 ms throttle and
+`IsPlayerReadyToMakeInventoryRequest`, emits `CM_Inventory::Event_UseEvent`,
+increments `ClientUISystem::m_cBusy`, and then calls
+`CPlayerSystem::UsingItem`. The confirmation callback has the same order.
+`CM_Item::DispatchUI_UseDone` routes event `0x01C7` to
+`Handle_Item__UseDone`, which decrements exactly one busy reference and updates
+the cursor when the count reaches zero.
+
+Therefore the invariant is:
+
+```text
+one accepted Use request that reached the wire
+    owns one busy reference
+    until one authoritative UseDone arrives
+```
+
+There is no retail timeout and movement cancellation is not a substitute for
+`UseDone` after dispatch.
+
+## ACE and protocol cross-reference
+
+- ACE `GameActionUseItem` and `Player_Use.TryUseItem` confirm that the Use
+  request owns the server-side operation and that every completed/rejected
+  operation returns `UseDone`.
+- ACE `Player_Move.CreateMoveToChain` confirms that the server may approach a
+  distant target before executing that operation.
+- holtburger `inventory/actions.rs` and `inventory/events.rs` independently
+  confirm the one Use action / one UseDone event protocol pair.
+
+The existing close-range compatibility seam is recorded as divergence AD-27:
+acdream may finish its local turn before emitting Use. That seam creates a
+real pre-wire interval which retail does not have, so it needs explicit
+ownership rather than pretending a server completion is already owed.
+
+## Ported ownership pseudocode
+
+```text
+BeginAcceptedUse(object):
+    reservation = BusyOwner.Reserve()
+    busyCount += 1
+    RequestUse(object, reservation)
+
+RequestUse(object, reservation):
+    if session/identity/approach is invalid:
+        reservation.CancelBeforeDispatch()
+        return
+
+    if a close-range turn must finish first:
+        pending = (exact object incarnation, approach token, reservation)
+        if movement installation fails:
+            pending.reservation.CancelBeforeDispatch()
+        return
+
+    if SendUse(object) succeeds:
+        reservation.MarkDispatched()
+    else:
+        reservation.CancelBeforeDispatch()
+
+OnNaturalApproachCompletion(pending):
+    if pending incarnation is stale:
+        pending.reservation.CancelBeforeDispatch()
+    else if SendUse(pending.object) succeeds:
+        pending.reservation.MarkDispatched()
+    else:
+        pending.reservation.CancelBeforeDispatch()
+
+OnApproachCancelledOrTargetRemoved(pending):
+    pending.reservation.CancelBeforeDispatch()
+
+reservation.MarkDispatched():
+    // Ownership transfers to the server completion. Keep busyCount unchanged.
+    make later local cancellation inert
+
+reservation.CancelBeforeDispatch():
+    // No packet exists, therefore no UseDone can arrive for this reservation.
+    busyCount -= 1
+    make duplicate cancellation inert
+
+OnUseDone(error):
+    busyCount -= 1
+    if busyCount == 0:
+        update cursor
+
+OnSessionReset():
+    invalidate the reservation generation
+    busyCount = 0
+```
+
+The reservation is idempotent and generation-bound. A late callback from a
+retired session cannot decrement a new session's busy reference.
+
+## Regression evidence
+
+The connected trace showed successful NPC Use packets and matching
+`UseDone(0)`. A managed heap snapshot after the final completion showed
+`ItemInteractionController._busyCount == 0`, no pending inventory request, and
+no pending auto-wield transaction. The permanent failure path was instead the
+pre-wire close-range branch: it incremented busy before local movement, but
+cancellation or stale identity discarded the pending send, leaving no packet
+and therefore no possible `UseDone`.