fix(ui): D.2b-B — address phase-boundary review (burden % saturation + equipped filter)

Opus phase-boundary review findings:
- I1 (faithfulness): LoadToPercent now computes from the CLAMPED fill
  (floor(LoadToFill(load)*300)), so the burden % SATURATES at 300% like retail
  (decomp 176544-176576 clamps arg2 to [0,1] BEFORE the *300). The old
  floor(load*100) over-read to 400% at 4x capacity. Golden test corrected.
- I2 (partition): exclude equipped items (CurrentlyEquippedLocation != None) from
  the contents grid + selector — a mid-session self-wield routes them through
  MoveItem(item, WielderGuid=player) into GetContents(player); retail's gm3DItemsUI
  shows pack contents only. New conformance test.
- N1: drop dead 'using System.Collections.Generic' (left after the 383e8b7 cleanup).
- N3: AP-48 risk wording (drift can be low OR high vs server EncumbranceVal).

Build green; BurdenMath 17, InventoryController/UiMeter 10 tests pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/AcDream.Core/Items/ClientObject.cs

@@ -258,12 +258,14 @@ public static class BurdenMath
     }
 
     /// <summary>
-    /// Retail <c>gmBackpackUI::SetLoadLevel</c> percent text (decomp 176576): after
-    /// <c>arg2 = load/3</c>, the text is <c>floor(arg2 * 300) = floor(load * 100)</c>,
-    /// NOT clamped (reads up to 300%+).
+    /// Retail <c>gmBackpackUI::SetLoadLevel</c> percent text (decomp 176542-176576): the
+    /// percent is computed from the CLAMPED fill — <c>arg2 = load/3</c> is clamped to [0,1]
+    /// (the 176544-176563 block sets <c>arg2 = 1.0</c> when fill &gt;= 1) BEFORE
+    /// <c>floor(arg2 * 300)</c>. So the number SATURATES at 300% (it does NOT read 400% at
+    /// 4x capacity). Equivalent to <c>floor(LoadToFill(load) * 300)</c>.
     /// </summary>
     public static int LoadToPercent(float load)
-        => (int)System.MathF.Floor(load * 100f);
+        => (int)System.MathF.Floor(LoadToFill(load) * 300f);
 
     public static int ComputeMax(int strength, int bonusBurden)
         => BurdenPerStrength * strength + strength * bonusBurden;