feat(runtime): Slice 5.3 — RuntimeInventoryState owns the vendor browse session

The sole VendorState joins the J4.2 inventory owners: populated by the
new 0x0062 ApproachVendor route (parse via VendorApproach, wire-to-
domain mapping at the routing seam, silent-drop on malformed like every
sibling), borrowed by both graphical and headless hosts, and torn down
through the EXISTING ExternalContainer reset stage — session reset,
portal-out, and logout all funnel through the one mechanism. Close is
client-local per retail (nothing on the wire): a range watcher rides
the existing per-advanced-frame publishMovement callback, using the
vendor's own authored UseRadius (ACE's 0.6 m fallback when absent).
The dormant ItemInteractionController ActiveVendorId seam is finally
wired as a live delegate — real id while open, 0 the moment the
session clears.

AP-160 filed in this same commit: the watcher measures plain 3D center
distance rather than retail's cylinder-gap, because Runtime has no
per-NPC collision radius/height source; bounded sub-meter, client-
local UI only.

Twelve Runtime tests: populate/field mapping, vendor replacement,
range clear + within-range retention, all three generation teardowns,
the ActiveVendorId seam, malformed-event drop. Clean-room complete
solution: 11,302 passed / 4 skipped / 0 failed.

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

src/AcDream.App/Net/LiveSessionRuntimeFactory.cs

@@ -286,7 +286,8 @@ internal sealed class LiveSessionRuntimeFactory
                 retailUi.HandleAppraisal(appraisal);
             else
                 _interaction.ItemInteraction.AcceptAppraisalResponse(appraisal.Guid);
-        });
+        },
+        Vendor: _domain.Inventory.Vendor);
 
     private LiveCharacterSessionBindings CreateCharacterBindings(
         SkillTable? skillTable)