[BenjaFriend]

Fixes #135.

What changed

• Transform dirty flag. SetPos, SetRotation, and SetScale set it. CalculateWorldMatrix clears it. A transform loaded from a level stays dirty. The editor calls MarkDirty() after it writes fields directly.
• Shared camera UBO. Projection and view moved out of the per-mesh UBO into one camera UBO (binding 5 in mrt.vert, .spv rebuilt). A camera move no longer dirties every mesh.
• Dirty-only UBO uploads. A mesh UBO is written only when its transform is dirty, or when the mesh is new or replaced.
• Cached offscreen command buffers. They are recorded again only when the draw list changes: MeshRenderer/Transform construct, destroy, or replace, or a swapchain resize.
• Editor model/material changes go through registry.replace(), so the renderer writes the new textures to the descriptor set. Before, a material change did not update the textures.

Testing

• ctest: 101/101 pass, including new FlingTests/Engine/TransformTests.cpp. Comment-style check passes.
• Sandbox on an RTX 3090 with VK_LAYER_KHRONOS_validation: Level_1 and the Sandbox lighting test with about 750 entities, rotating and moving objects, and a sphere spawned at runtime. 0 validation messages, and rendering is correct.

Follow-ups (not in this PR)

• The UBO pass still checks every mesh's dirty flag. It is cheap, but a dirty list kept by registry signals would remove that loop. All transform writes would then have to go through the registry.
• The engine's EnableValidationLayers=true config fails to create the instance on this machine ("layers requested but not available"). I tested with VK_INSTANCE_LAYERS instead.

🤖 Generated with Claude Code

https://claude.ai/code/session_01E5zLKAKV1AEmphy4e2YToX