Fix GPU resource leaks and re-entrant world loading for instance transitions

Reset descriptor pools in CharacterRenderer/M2Renderer/WMORenderer on map
change to prevent VK_ERROR_DEVICE_LOST from pool exhaustion. Defer re-entrant
SMSG_NEW_WORLD during active world load to avoid recursive cleanup crashes.
Gate swim bubbles on swimming state, skip redundant shadow pipeline re-init,
add WOWEE_SKIP_* env vars for render isolation debugging.

include/core/application.hpp

@@ -9,6 +9,7 @@
 #include <unordered_map>
 #include <unordered_set>
 #include <array>
+#include <optional>
 
 namespace wowee {
 
@@ -189,6 +190,12 @@ private:
     uint32_t wyvernDisplayId_ = 0;
     bool lastTaxiFlight_ = false;
     uint32_t loadedMapId_ = 0xFFFFFFFF;  // Map ID of currently loaded terrain (0xFFFFFFFF = none)
+    uint32_t worldLoadGeneration_ = 0;   // Incremented on each world entry to detect re-entrant loads
+    bool loadingWorld_ = false;          // True while loadOnlineWorldTerrain is running
+    struct PendingWorldEntry {
+        uint32_t mapId; float x, y, z;
+    };
+    std::optional<PendingWorldEntry> pendingWorldEntry_;  // Deferred world entry during loading
     float taxiLandingClampTimer_ = 0.0f;
     float worldEntryMovementGraceTimer_ = 0.0f;
     float facingSendCooldown_ = 0.0f;        // Rate-limits MSG_MOVE_SET_FACING

include/rendering/character_renderer.hpp

@@ -48,6 +48,7 @@ public:
                     VkRenderPass renderPassOverride = VK_NULL_HANDLE,
                     VkSampleCountFlagBits msaaSamples = VK_SAMPLE_COUNT_1_BIT);
     void shutdown();
+    void clear();  // Remove all models/instances/textures but keep pipelines/pools
 
     void setAssetManager(pipeline::AssetManager* am) { assetManager = am; }
 

include/rendering/m2_renderer.hpp

@@ -254,6 +254,7 @@ public:
      * Initialize shadow pipeline (Phase 7)
      */
     bool initializeShadow(VkRenderPass shadowRenderPass);
+    bool hasShadowPipeline() const { return shadowPipeline_ != VK_NULL_HANDLE; }
 
     /**
      * Render depth-only pass for shadow casting