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/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.