refactor: consolidate duplicate environment variable utility functions

Move envSizeMBOrDefault and envSizeOrDefault from 4 separate rendering
modules (character_renderer, m2_renderer, terrain_renderer, wmo_renderer)
into shared vk_utils.hpp header as inline functions. Use the most robust
version which includes overflow checking for MB-to-bytes conversion. This
eliminates 7 identical local function definitions and improves consistency
across all rendering modules.

include/rendering/vk_utils.hpp

@@ -3,6 +3,8 @@
 #include <vulkan/vulkan.h>
 #include <vk_mem_alloc.h>
 #include <cstdint>
+#include <limits>
+#include <cstdlib>
 
 namespace wowee {
 namespace rendering {
@@ -56,5 +58,25 @@ inline bool vkCheck(VkResult result, [[maybe_unused]] const char* msg) {
     return true;
 }
 
+// Environment variable utility functions
+inline size_t envSizeMBOrDefault(const char* name, size_t defMb) {
+    const char* v = std::getenv(name);
+    if (!v || !*v) return defMb;
+    char* end = nullptr;
+    unsigned long long mb = std::strtoull(v, &end, 10);
+    if (end == v || mb == 0) return defMb;
+    if (mb > (std::numeric_limits<size_t>::max() / (1024ull * 1024ull))) return defMb;
+    return static_cast<size_t>(mb);
+}
+
+inline size_t envSizeOrDefault(const char* name, size_t defValue) {
+    const char* v = std::getenv(name);
+    if (!v || !*v) return defValue;
+    char* end = nullptr;
+    unsigned long long n = std::strtoull(v, &end, 10);
+    if (end == v || n == 0) return defValue;
+    return static_cast<size_t>(n);
+}
+
 } // namespace rendering
 } // namespace wowee

src/rendering/character_renderer.cpp

@@ -46,25 +46,6 @@ namespace wowee {
 namespace rendering {
 
 namespace {
-size_t envSizeMBOrDefault(const char* name, size_t defMb) {
-    const char* v = std::getenv(name);
-    if (!v || !*v) return defMb;
-    char* end = nullptr;
-    unsigned long long mb = std::strtoull(v, &end, 10);
-    if (end == v || mb == 0) return defMb;
-    if (mb > (std::numeric_limits<size_t>::max() / (1024ull * 1024ull))) return defMb;
-    return static_cast<size_t>(mb);
-}
-
-size_t envSizeOrDefault(const char* name, size_t defValue) {
-    const char* v = std::getenv(name);
-    if (!v || !*v) return defValue;
-    char* end = nullptr;
-    unsigned long long n = std::strtoull(v, &end, 10);
-    if (end == v || n == 0) return defValue;
-    return static_cast<size_t>(n);
-}
-
 size_t approxTextureBytesWithMips(int w, int h) {
     if (w <= 0 || h <= 0) return 0;
     size_t base = static_cast<size_t>(w) * static_cast<size_t>(h) * 4ull;

src/rendering/m2_renderer.cpp

@@ -40,24 +40,6 @@ bool envFlagEnabled(const char* key, bool defaultValue) {
     return !(v == "0" || v == "false" || v == "off" || v == "no");
 }
 
-size_t envSizeMBOrDefault(const char* name, size_t defMb) {
-    const char* raw = std::getenv(name);
-    if (!raw || !*raw) return defMb;
-    char* end = nullptr;
-    unsigned long long mb = std::strtoull(raw, &end, 10);
-    if (end == raw || mb == 0) return defMb;
-    return static_cast<size_t>(mb);
-}
-
-size_t envSizeOrDefault(const char* name, size_t defValue) {
-    const char* raw = std::getenv(name);
-    if (!raw || !*raw) return defValue;
-    char* end = nullptr;
-    unsigned long long v = std::strtoull(raw, &end, 10);
-    if (end == raw || v == 0) return defValue;
-    return static_cast<size_t>(v);
-}
-
 static constexpr uint32_t kParticleFlagRandomized = 0x40;
 static constexpr uint32_t kParticleFlagTiled = 0x80;
 

src/rendering/terrain_renderer.cpp

@@ -20,17 +20,6 @@
 namespace wowee {
 namespace rendering {
 
-namespace {
-size_t envSizeMBOrDefault(const char* name, size_t defMb) {
-    const char* raw = std::getenv(name);
-    if (!raw || !*raw) return defMb;
-    char* end = nullptr;
-    unsigned long long mb = std::strtoull(raw, &end, 10);
-    if (end == raw || mb == 0) return defMb;
-    return static_cast<size_t>(mb);
-}
-} // namespace
-
 // Matches set 1 binding 7 in terrain.frag.glsl
 struct TerrainParamsUBO {
     int32_t layerCount;

src/rendering/wmo_renderer.cpp

@@ -29,23 +29,6 @@ namespace wowee {
 namespace rendering {
 
 namespace {
-size_t envSizeMBOrDefault(const char* name, size_t defMb) {
-    const char* raw = std::getenv(name);
-    if (!raw || !*raw) return defMb;
-    char* end = nullptr;
-    unsigned long long mb = std::strtoull(raw, &end, 10);
-    if (end == raw || mb == 0) return defMb;
-    return static_cast<size_t>(mb);
-}
-
-size_t envSizeOrDefault(const char* name, size_t defValue) {
-    const char* raw = std::getenv(name);
-    if (!raw || !*raw) return defValue;
-    char* end = nullptr;
-    unsigned long long v = std::strtoull(raw, &end, 10);
-    if (end == raw || v == 0) return defValue;
-    return static_cast<size_t>(v);
-}
 } // namespace
 
 // Thread-local scratch buffers for collision queries (allows concurrent getFloorHeight/checkWallCollision calls)