Stabilize Vulkan shadow pipeline diagnostics and compatibility path

- Fix shadow depth image layout transitions by tracking per-frame old/new layouts.
- Update receiver shadow projection to Vulkan clip-depth convention.
- Test inverted shadow compare op path (GREATER_OR_EQUAL).
- Switch shadow compare samplers to NEAREST filtering for broader Vulkan compatibility.
- Expand shadow caster coverage by disabling caster cull filtering in WMO/M2/Character shadow pipelines.
- Keep light-space matrix path on stable character-centered framing.

include/rendering/renderer.hpp

@@ -233,6 +233,7 @@ private:
     VkSampler shadowSampler = VK_NULL_HANDLE;
     VkRenderPass shadowRenderPass = VK_NULL_HANDLE;
     VkFramebuffer shadowFramebuffer = VK_NULL_HANDLE;
+    VkImageLayout shadowDepthLayout_ = VK_IMAGE_LAYOUT_UNDEFINED;
     glm::mat4 lightSpaceMatrix = glm::mat4(1.0f);
     glm::vec3 shadowCenter = glm::vec3(0.0f);
     bool shadowCenterInitialized = false;