- Fix move constructor and move assignment: set other.ownsSampler_ to
false after transfer (was incorrectly set to true, leaving moved-from
object claiming ownership of a null sampler)
- Fix destroy(): reset ownsSampler_ to false after clearing sampler
handle (was set to true, inconsistent with null handle state)
- Extract finalizeSampler() from 3 duplicated cache-or-create blocks
in createSampler() overloads and createShadowSampler() (-24 lines)
- Add SPIR-V alignment why-comment in vk_shader.cpp
