Re-allocate megaBoneSet_[0..1] in M2Renderer::clear() after vkResetDescriptorPool invalidates all
sets from boneDescPool_. Stale handles were bound to command buffers during rendering, causing
cascading validation errors. Also add ImGui::Dummy() after SetCursorScreenPos in the shaman totem
bar to satisfy ImGui's window boundary extension assertion.
M2Renderer::clear() reset descriptor pools but left the texture cache
and failed-texture tracking intact. On re-login the stale cache filled
the budget, failedTextureRetryAt_ blocked reloads, and the client
entered an infinite model-load loop. Match the cleanup already done in
shutdown() and CharacterRenderer::clear().