fix(vendor): re-gate residuals — MaxStackSize is the stack operand, wire-authored use radius, purse summaries

R1 the split bar's operand is the item's authored MaxStackSize —
three retail sites read pwd._maxStackSize directly (InqListSlotCount
pc:200052, buy-button cases pc:203996/204086) where ACE never fills
the desc stack and standard stock is unlimited. Threaded StackSizeMax
end to end with one shared resolver; the two literal _maxStackSize
sites are now byte-exact; AP-165 retired, AP-169 corrected.
R2 walk-to-vendor never opened because GetUseRadius used an UNCITED
3m Creature heuristic as the local stop distance while ACE's poll
demands the authored radius (default 0.6 m) — the walk stopped and
the Use fired far outside acceptance. Now reads the wire-authored
spawn UseRadius with ACE's exact fallback; heuristic constants
deleted. A first sabotage attempt was non-discriminating
(coincidental 0.6) and was corrected — the discriminating version is
what landed.
R3 the Buying/Selling purse summaries ("Buying %d %s worth %hsp" /
"You have %hsp") recovered from the binary data segment where BN
mis-attributes the Buy-side literal; wired to staging and money
changes on the four authored text elements; AP-166 narrowed to the
pending-sell highlight.

Clean-room complete solution: 11,528 passed / 4 skipped / 0 failed.

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

src/AcDream.Runtime/Gameplay/VendorShopItemMaterializer.cs

@@ -226,9 +226,9 @@ public sealed class VendorShopItemMaterializer : IDisposable
     /// the wire-shaped merge patch <see cref="ClientObjectTable.Ingest"/>
     /// expects.
     /// <para>
-    /// G2 gate-finding fix (2026-08-08, register AP-169): retail's own
-    /// client (<c>gmToolbarUI::HandleSelectionChanged</c>, <c>pc:198688</c>/
-    /// <c>198744</c>/<c>198774</c>/<c>198791</c>) reads
+    /// R1 gate-finding fix (2026-08-08, register AP-169 correction): retail's
+    /// own client (<c>gmToolbarUI::HandleSelectionChanged</c>,
+    /// <c>pc:198688</c>/<c>198744</c>/<c>198774</c>/<c>198791</c>) reads
     /// <c>eax_5-&gt;pwd._stackSize</c> — our <see cref="VendorShopItem.DescStackSize"/>
     /// — uniformly for BOTH owned-inventory and vendor-owned selections to
     /// decide whether the toolbar split slider shows and what it caps at.
@@ -246,18 +246,28 @@ public sealed class VendorShopItemMaterializer : IDisposable
     /// for every vendor listing. Reading only <c>DescStackSize</c> here
     /// therefore left <see cref="ClientObject.StackSize"/> at its default
     /// for every materialized shop item, so the toolbar split slider never
-    /// appeared for ANY vendor stack, matching the live report exactly (it
-    /// DID appear for owned-inventory stacks, which ACE populates normally
-    /// via ordinary pickup/loot <c>SetStackSize</c> calls). This now prefers
-    /// <c>DescStackSize</c> when present (retail-faithful first, and
-    /// forward-compatible with any server that DOES populate it), falling
-    /// back to the packed <c>StackSize</c> supply-count field clamped to a
-    /// sane positive bound — the field that IS reliably populated against
-    /// ACE. The <c>StackSize == -1</c> (unlimited-supply) sentinel has no
-    /// bounded per-row purchase cap in <see cref="VendorShopItem"/>'s wire
-    /// shape today (no <c>_maxStackSize</c> field carried), so it falls
-    /// through to the conservative "1" default rather than inventing an
-    /// arbitrary ceiling — see the register.
+    /// appeared for ANY vendor stack.
+    /// </para>
+    /// <para>
+    /// <b>The G2 packed-supply-count fallback (retired 2026-08-08).</b> An
+    /// earlier fix fell back to <see cref="VendorShopItem.StackSize"/> (the
+    /// packed ItemProfile "how many for sale" dword) when
+    /// <c>DescStackSize</c> was absent. That did not survive live testing —
+    /// a standard vendor listing (e.g. a Prismatic Taper) has UNLIMITED
+    /// stock (<c>StackSize == -1</c>), so the fallback produced nothing
+    /// usable and the bar stayed hidden, matching the live report exactly
+    /// (bare "Prismatic Taper", no bar, no count). The live retail
+    /// screenshot showed "1000 Prismatic Tapers" with the bar visible and a
+    /// ceiling of 1000 — 1000 being the taper's authored MAX STACK SIZE, not
+    /// any bounded supply count. This now prefers <c>DescStackSize</c> when
+    /// present (retail-faithful first, forward-compatible with any server
+    /// that DOES populate it), falling back to
+    /// <see cref="VendorShopItem.MaxStackSize"/> — the item TYPE's authored
+    /// stack ceiling, which ACE DOES populate (an ordinary weenie property)
+    /// and which a real retail server evidently uses AS <c>_stackSize</c>
+    /// for an unlimited-supply "one full stack" browse listing. See
+    /// <see cref="VendorSplitPolicy.ResolveAuthoredStackSize"/> and the
+    /// register, AP-169.
     /// </para>
     /// <para>
     /// Every other field <see cref="VendorShopItem"/> doesn't carry
@@ -276,8 +286,8 @@ public sealed class VendorShopItemMaterializer : IDisposable
         IconUnderlayId: item.IconUnderlayId,
         Effects: item.Effects,
         Value: item.Value,
-        StackSize: ResolveDisplayStackSize(item),
-        StackSizeMax: null,
+        StackSize: VendorSplitPolicy.ResolveAuthoredStackSize(item.DescStackSize, item.MaxStackSize),
+        StackSizeMax: item.MaxStackSize,
         Burden: null,
         ContainerId: vendorId,
         WielderId: 0u,
@@ -291,23 +301,6 @@ public sealed class VendorShopItemMaterializer : IDisposable
         Workmanship: null,
         PluralName: item.PluralName);
 
-    /// <summary>
-    /// G2 fix: <see cref="VendorShopItem.DescStackSize"/> when the wire
-    /// actually carried it (nonzero — a genuinely retail-faithful server),
-    /// else the packed <see cref="VendorShopItem.StackSize"/> supply count
-    /// (what ACE reliably sends) when it names a real bounded quantity,
-    /// else 1 (non-splittable — the safe default for the unlimited-supply
-    /// sentinel or a genuinely single-unit listing).
-    /// </summary>
-    private static int? ResolveDisplayStackSize(VendorShopItem item)
-    {
-        if (item.DescStackSize is { } desc && desc > 0)
-            return desc;
-        if (item.StackSize > 0)
-            return item.StackSize;
-        return 1;
-    }
-
     public void Dispose()
     {
         if (_disposed) return;