feat(vendor): Slice 6 buy arc — shop items are real objects, vendor selection is THE selection, and Buy works (0x005F)

Three ordered pieces in one landing (the shared controller/composition
files carry all three; the internal order was 6.1 -> 6.2 -> 6.3):

6.1 VendorShopItemMaterializer diff-merges the shop list into the live
ClientObjectTable on VendorState transitions (so client-local close and
session teardown retire the entries too) and never claims a guid it did
not add — ACE's UniqueItemsForSale can re-list a guid a player once
held (AP-163 files the collision-skip; no retail counterpart traced).
Right-click examine on shop items now routes through the ordinary
appraisal path — the 5.4 F7c blocker dissolves with the table entries.

6.2 SelectionChangeSource.Vendor: row clicks, auto-select, and examine
all flow through the canonical SelectionState; the status bar and the
existing byte-faithful StackSplitQuantityState slider light up
unmodified. VendorSplitPolicy is the single 0xDC41CB0 mask owner; the
slider VALUE seeds to 1 for exempt items while maxSplitSize keeps the
stack (the splitSize/maxSplitSize distinction, research §B.3).
Selection clears at retail's actual site — VendorItemsUI::RemoveFromShop
(pc:202848), not a CloseVendor-level clear that does not exist.

6.3 BuildBuy (0x005F): vendorGuid, count, (i32 amount, u32 guid) pairs,
and the trailing alternateCurrencyId the REAL client sends
(CM_Vendor::Event_Buy pc:689288) though ACE's reader ignores it.
TryBuy rides the EXISTING J5.2 one-request-at-a-time reservation and
completes on UseDone; the Buy button disables while a request is in
flight. The reconciliation round-trip (money property update, inventory
CreateObject, ApproachVendor refresh -> panel rebuild) is proven by a
synthetic-inbound test against existing machinery — no new owner.

Register: AP-161 narrowed (selection + examine residuals close;
staging/Sell remain; double-click-to-buy confirmed ABSENT from retail
with negative evidence cited — we match retail). AP-162 files the
conscious no-client-side-affordability-precheck deferral.

Clean-room complete solution: 11,368 passed / 4 skipped / 0 failed.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

tests/AcDream.Runtime.Tests/Gameplay/RuntimeVendorLifecycleTests.cs

@@ -198,6 +198,56 @@ public sealed class RuntimeVendorLifecycleTests
         Assert.Equal(0u, runtime.InventoryOwner.Vendor.VendorId);
     }
 
+    [Fact]
+    public void ApproachVendorEvent_MaterializesShopItemsIntoTheOwnedObjectTable()
+    {
+        // Slice 6.1: unlike Wire()'s throwaway ClientObjectTable (used by
+        // the tests above, which only assert on VendorState itself), this
+        // wires the dispatcher against the SAME table
+        // RuntimeInventoryState.Objects exposes, so the
+        // VendorShopItemMaterializer subscription RuntimeInventoryState's
+        // constructor installs is exercised end-to-end from the real wire
+        // parse through to ClientObjectTable.
+        using GameRuntime runtime = Create();
+        using IDisposable wiring = GameEventWiring.WireAll(
+            _dispatcher,
+            runtime.InventoryOwner.Objects,
+            new CombatState(),
+            new Spellbook(),
+            new ChatLog(),
+            vendor: runtime.InventoryOwner.Vendor);
+
+        Dispatch(BuildApproachVendorPayload(
+            vendorGuid: 0x40001000u,
+            categories: 0u, minValue: 0u, maxValue: 0u, dealsMagic: false,
+            buyPrice: 1f, sellPrice: 1f, currencyWcid: 0u, currencyAmount: 0u,
+            currencyName: "",
+            items:
+            [
+                new VendorItemFixture(
+                    0x50002000u, 1, "Iron Sword", 42u, 0x1234u,
+                    (uint)ItemType.Weapon, 250),
+            ]));
+
+        ClientObject? shopItem = runtime.InventoryOwner.Objects.Get(0x50002000u);
+        Assert.NotNull(shopItem);
+        Assert.Equal(0x40001000u, shopItem!.ContainerId);
+        Assert.Equal("Iron Sword", shopItem.Name);
+        Assert.Equal(1, runtime.InventoryOwner.VendorItems.OwnedCount);
+
+        runtime.InventoryOwner.Vendor.Close();
+
+        Assert.Null(runtime.InventoryOwner.Objects.Get(0x50002000u));
+        Assert.Equal(0, runtime.InventoryOwner.VendorItems.OwnedCount);
+        // Close() is a client-local session end, not full disposal, so only
+        // the vendor-specific ownership dimensions are asserted here — the
+        // full IsConverged gate is exercised by DisposingInventoryOwner_
+        // ClearsTheOpenVendorSession below.
+        RuntimeInventoryOwnershipSnapshot snapshot = runtime.InventoryOwner.CaptureOwnership();
+        Assert.Equal(0u, snapshot.VendorId);
+        Assert.Equal(0, snapshot.MaterializedVendorItemCount);
+    }
+
     [Fact]
     public void VendorId_IsTheLiveActiveVendorIdSeamSource()
     {