feat: show corpse skull marker on world map when player is a ghost

When the player dies and releases spirit, the world map now renders a
bone-white X cross at the corpse's location (matching the existing
minimap skull marker). The marker appears only when the player is a
ghost with an unclaimed corpse on the same map, and shows a "Your
corpse" tooltip on hover. Implemented via setCorpsePos() on WorldMap,
called from renderWorldMap() using getCorpseCanonicalPos().

include/rendering/world_map.hpp

@@ -67,6 +67,13 @@ public:
     void setServerExplorationMask(const std::vector<uint32_t>& masks, bool hasData);
     void setPartyDots(std::vector<WorldMapPartyDot> dots) { partyDots_ = std::move(dots); }
     void setTaxiNodes(std::vector<WorldMapTaxiNode> nodes) { taxiNodes_ = std::move(nodes); }
+    /// Set the player's corpse position for overlay rendering.
+    /// @param hasCorpse  True when the player is a ghost with an unclaimed corpse on this map.
+    /// @param renderPos  Corpse position in render-space coordinates.
+    void setCorpsePos(bool hasCorpse, glm::vec3 renderPos) {
+        hasCorpse_ = hasCorpse;
+        corpseRenderPos_ = renderPos;
+    }
     bool isOpen() const { return open; }
     void close() { open = false; }
 
@@ -141,6 +148,10 @@ private:
     std::vector<WorldMapTaxiNode> taxiNodes_;
     int currentMapId_ = -1;  ///< WoW map ID currently loaded (set in loadZonesFromDBC)
 
+    // Corpse marker (ghost state — set each frame from the UI layer)
+    bool      hasCorpse_        = false;
+    glm::vec3 corpseRenderPos_  = {};
+
     // Exploration / fog of war
     std::vector<uint32_t> serverExplorationMask;
     bool hasServerExplorationMask = false;