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.Core/Combat/CombatState.cs

@@ -92,6 +92,16 @@ public sealed class CombatState
     public float GetHealthPercent(uint guid) =>
         _healthByGuid.TryGetValue(guid, out var pct) ? pct : 1f;
 
+    /// <summary>
+    /// True if an UpdateHealth (0x01C0) has ever been received for this guid — i.e. the
+    /// server has reported real health for it (via damage broadcast or a successful
+    /// assess/QueryHealth reply). Distinguishes a known value from the 1.0 default that
+    /// <see cref="GetHealthPercent"/> returns for unseen guids. Used by the selected-object
+    /// meter to gate visibility (retail shows the bar only once health is known —
+    /// gmToolbarUI::RecvNotice_UpdateObjectHealth, acclient_2013_pseudo_c.txt:196213).
+    /// </summary>
+    public bool HasHealth(uint guid) => _healthByGuid.ContainsKey(guid);
+
     public int TrackedTargetCount => _healthByGuid.Count;
 
     // ── Inbound handlers (wired from WorldSession.GameEvents) ────────────────