fix(D.5.3a): selected-object meter visual-gate fixes (name, gate, flash, magenta)

Visual gate against retail surfaced several fidelity gaps in the selected-object
strip; all fixed and user-confirmed. Faithful to gmToolbarUI::HandleSelectionChanged
(acclient_2013_pseudo_c.txt:198635) + RecvNotice_UpdateObjectHealth (:196213).

- UiMeter.DrawHBar: guard each slice on `id != 0` BEFORE resolve. resolve(0)
  returns the 1x1 magenta placeholder with a non-zero GL handle, so the single-
  image meter (caps id=0) was drawing 1px magenta caps at the bar's ends. The
  3-slice vitals meter (all ids set) was unaffected. (the magenta-lines bug)
- SelectedObjectController: meter visibility is now UpdateHealth-driven (shown when
  health is known for the selected guid — HasHealth at select or HealthChanged),
  not shown-on-select; brief green selection flash via Tick revert; overlay floated
  above the meter so the flash isn't hidden by the bar; name top-aligned into the
  bar sprite's black band (NameBandHeight) with the bar below.
- GameWindow.IsHealthBarTarget: gate the health bar on the server PWD bits
  BF_ATTACKABLE (0x10) | BF_PLAYER (0x8) — friendly/vendor NPCs and attackable
  Doors (Misc type) are name-only; players/monsters get the bar. Replaces the
  too-loose IsLiveCreatureTarget. Wired SelectedObjectController.Tick in OnUpdate.
- CombatState.HasHealth(guid): distinguishes a known health value from the 1.0
  default, so a re-selected already-assessed target shows its bar immediately.
- TextureCache.GetOrUploadRenderSurface: resolve the surface's DefaultPaletteId
  so paletted (P8/INDEX16) UI sprites decode instead of falling to magenta.
- ToolbarController.HiddenIds: also hide 0x100001A3 (stack-entry box) — retail
  hides it in HandleSelectionChanged; it was rendering as a stray black box.

Divergence register: AP-47 (meter-visible timing) retired (now faithful); AP-46
rewritten to the BF_ATTACKABLE/BF_PLAYER gate approximation. Full suite green
(2,688 passed / 4 skipped). User-confirmed: name on top, NPC name-only, monster
bar on assess, green flash, no magenta.

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

src/AcDream.App/Rendering/TextureCache.cs

@@ -121,9 +121,11 @@ public sealed unsafe class TextureCache : Wb.ITextureCachePerInstance, IDisposab
     /// Surface→SurfaceTexture chain that <see cref="GetOrUpload(uint)"/> uses
     /// for world-geometry materials. This is the correct path for retail UI
     /// chrome + font glyph sheets, which reference RenderSurface directly.
-    /// Palette is null for now (a paletted INDEX16/P8 UI sprite would return
-    /// Magenta — wire a UI palette when one is actually encountered). Returns a
-    /// 1x1 magenta handle on miss.
+    /// Paletted (PFID_P8 / PFID_INDEX16) UI sprites — e.g. the selected-object
+    /// health-bar track 0x0600193E — are decoded against the RenderSurface's own
+    /// <c>DefaultPaletteId</c> (same starting palette <see cref="DecodeFromDats"/>
+    /// uses); non-paletted formats have DefaultPaletteId==0 → palette null. Returns
+    /// a 1x1 magenta handle on miss.
     /// </summary>
     public uint GetOrUploadRenderSurface(uint renderSurfaceId, out int width, out int height, bool nearest = false)
     {
@@ -138,7 +140,14 @@ public sealed unsafe class TextureCache : Wb.ITextureCachePerInstance, IDisposab
         if (_dats.Portal.TryGet<RenderSurface>(renderSurfaceId, out var rs)
             || _dats.HighRes.TryGet<RenderSurface>(renderSurfaceId, out rs))
         {
-            decoded = SurfaceDecoder.DecodeRenderSurface(rs, palette: null);
+            // Resolve the surface's own default palette so paletted UI sprites decode
+            // correctly instead of the magenta fallback (the back-track 0x0600193E behind
+            // the selected-object health bar is PFID_P8/INDEX16). Non-paletted formats
+            // (DefaultPaletteId==0) keep the previous null-palette behaviour unchanged.
+            Palette? palette = rs.DefaultPaletteId != 0
+                ? _dats.Get<Palette>(rs.DefaultPaletteId)
+                : null;
+            decoded = SurfaceDecoder.DecodeRenderSurface(rs, palette);
         }
         else
         {