fix(vendor): evidence-based pass — max-first stack ceiling; the local player resolves never-animated MoveTo targets

Both chains pinned by the live [vendor-diag] run (vendor-diag.log)
after three code-reading rounds each failed:

The split bar: ACE serializes descStackSize=1 for EVERY browse row
(live wire, log 343-348) — the R1-era "ACE never populates desc"
claim is retracted with the line quoted. Retail's vendor sites read
pwd._maxStackSize directly (four sites, incl. UpdateItemsList
@0x004c1ea0 stamping min(remaining, _maxStackSize));
ResolveAuthoredStackSize flips to max-first for its vendor-only
consumers. Taper ceiling 1000, scarab 100, seed 1 for exempt.
Pricing still reads the desc (per-1 values on ACE).

Walk-to-use: the local player's getObjectA seam was bound to
TryGetPhysicsHost, which resolves only INSTALLED physics hosts — a
never-animated vendor has none, so TargetManager.SetTarget got null,
the MoveToObject armed with zero nodes, and UseTime never dispatched.
The log's natural=False completions were the user's own movement keys
(retail-correct input-edge cancels); attempt 4 worked because the
greeting animation had installed a host. RuntimePhysicsState gains
the retail CObjectMaint::GetObjectA seam (bound canonical resolver
with installed-host fallback); the graphical host binds the SAME
lazy-minimal-host resolver every remote already uses — whose own doc
comment names this exact never-animated hazard. The reservation
release was already correct (2b premise refuted with evidence); the
production-wiring invariants are now pinned by four new tests
including the pre-fix pathology as a permanent sabotage control.

AP-169 rewritten a second time, honestly. The [vendor-diag] probe
family (ACDREAM_DUMP_VENDOR) lands env-gated for future live triage.

Clean-room complete solution: 11,536 passed / 4 skipped / 0 failed.

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

src/AcDream.App/UI/ItemInteractionController.cs

@@ -509,6 +509,11 @@ public sealed class ItemInteractionController : IDisposable
         switch (mode)
         {
             case InteractionModeKind.Use:
+                if (VendorDiagnostics.DumpVendorEnabled)
+                {
+                    Console.WriteLine(
+                        $"[vendor-diag] route=target-mode-click OfferPrimaryClick(Use) guid=0x{targetGuid:X8}");
+                }
                 ClearTargetMode();
                 accepted = ActivateItem(targetGuid);
                 break;
@@ -541,6 +546,11 @@ public sealed class ItemInteractionController : IDisposable
     /// </summary>
     public bool UseSelectedOrEnterMode(uint selectedObjectId)
     {
+        if (VendorDiagnostics.DumpVendorEnabled)
+        {
+            Console.WriteLine(
+                $"[vendor-diag] route=toolbar-or-queued-use UseSelectedOrEnterMode guid=0x{selectedObjectId:X8}");
+        }
         if (selectedObjectId != 0)
             return ActivateItem(selectedObjectId);
         return _interactionState.EnterUse();
@@ -640,6 +650,11 @@ public sealed class ItemInteractionController : IDisposable
 
     public bool ActivateItem(uint itemGuid)
     {
+        if (VendorDiagnostics.DumpVendorEnabled)
+        {
+            Console.WriteLine(
+                $"[vendor-diag] entry:ActivateItem guid=0x{itemGuid:X8} isTargetModeActive={IsTargetModeActive}");
+        }
         if (itemGuid == 0) return false;
 
         if (IsTargetModeActive)
@@ -966,6 +981,11 @@ public sealed class ItemInteractionController : IDisposable
     /// </summary>
     public bool ExecuteConfirmedUse(uint objectId)
     {
+        if (VendorDiagnostics.DumpVendorEnabled)
+        {
+            Console.WriteLine(
+                $"[vendor-diag] route=confirmed-use ExecuteConfirmedUse guid=0x{objectId:X8}");
+        }
         if (objectId == 0u || (_requestUse is null && _sendUse is null))
             return false;
         if (!EnsureInventoryRequestReady())

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

@@ -346,6 +346,13 @@ public sealed class SelectedObjectController : IRetainedPanelController
             ? $"{stackSize} {objectName}"
             : objectName;
 
+        if (VendorDiagnostics.DumpVendorEnabled)
+        {
+            Console.WriteLine(
+                $"[vendor-diag] ApplySelection guid=0x{g:X8} stackSizeOperand={stackSize} "
+                + $"objectName={objectName ?? "null"} builtLabel={_currentName ?? "null"}");
+        }
+
         // ── 3. Selection overlay: brief flash (retail container ObjectSelected
         //       = Pause(0.25s)→Normal). "StackedItemSelected" for stacks. ──────────────
         SetOverlayState(stackSize > 1u
@@ -367,10 +374,23 @@ public sealed class SelectedObjectController : IRetainedPanelController
         // starting VALUE differs, not the ceiling.
         if (stackSize > 1u)
         {
-            uint seed = _isVendorSplitExempt(g) ? 1u : stackSize;
+            bool vendorSplitExempt = _isVendorSplitExempt(g);
+            uint seed = vendorSplitExempt ? 1u : stackSize;
             _splitQuantity.Reset(stackSize, initialValue: seed);
             if (_stackSizeEntry is not null) _stackSizeEntry.Visible = true;
             if (_stackSizeSlider is not null) _stackSizeSlider.Visible = true;
+            if (VendorDiagnostics.DumpVendorEnabled)
+            {
+                Console.WriteLine(
+                    $"[vendor-diag] ApplySelection guid=0x{g:X8} sliderVisible=true "
+                    + $"isVendorSplitExempt={vendorSplitExempt} maxSplitSize={stackSize} seed={seed}");
+            }
+        }
+        else if (VendorDiagnostics.DumpVendorEnabled)
+        {
+            Console.WriteLine(
+                $"[vendor-diag] ApplySelection guid=0x{g:X8} sliderVisible=false "
+                + $"failingPredicate=stackSize<=1u stackSize={stackSize}");
         }
 
         // ── 4. Health: query, and show the meter only if real health is already known.

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

@@ -1401,15 +1401,18 @@ public sealed class VendorUiController : IRetainedPanelController, IItemListDrag
     /// this one — otherwise the CURRENT slider value via
     /// <c>ItemHolder::GetObjectSplitSize</c> (<c>0x00586F00</c>).
     /// <para>
-    /// R1 gate-finding fix (2026-08-08, register AP-169 correction): the
-    /// ceiling this gates on is <see cref="VendorSplitPolicy.ResolveAuthoredStackSize"/>
-    /// — <see cref="VendorShopItem.DescStackSize"/> when the wire carries
-    /// it, else <see cref="VendorShopItem.MaxStackSize"/> — the SAME
-    /// resolution <see cref="VendorShopItemMaterializer"/> uses to seed
-    /// <see cref="ClientObject.StackSize"/> (and therefore the toolbar
-    /// slider's own ceiling, <c>SelectedObjectController</c>). Using a
-    /// narrower source here than the visible slider would let the slider
-    /// show a ceiling of 1000 while every Buy still sent quantity 1.
+    /// R1 gate-finding fix, CORRECTED at the 2026-08-08 live-evidence
+    /// re-fix (register AP-169, second correction): the ceiling this gates
+    /// on is <see cref="VendorSplitPolicy.ResolveAuthoredStackSize"/> —
+    /// <see cref="VendorShopItem.MaxStackSize"/> FIRST (retail's own
+    /// vendor-owned quantity operand: the Buy cases at
+    /// <c>pc:203996</c>/<c>204086</c> gate on <c>pwd._maxStackSize &gt; 1</c>
+    /// literally), falling back to <see cref="VendorShopItem.DescStackSize"/>
+    /// — the SAME resolution <see cref="VendorShopItemMaterializer"/> uses
+    /// to seed <see cref="ClientObject.StackSize"/> (and therefore the
+    /// toolbar slider's own ceiling, <c>SelectedObjectController</c>).
+    /// Using a narrower source here than the visible slider would let the
+    /// slider show a ceiling of 1000 while every Buy still sent quantity 1.
     /// </para>
     /// </summary>
     private uint ResolveBuyQuantity(VendorShopItem item)