Fix Vulkan renderer

[tdecroyere]

Fix the Vulkan renderer incrementally after the Vulkan 1.4.357 upgrade.

Current fixes:

• clamp SystemDataPool commit batches to the number of items actually remaining in the pool, avoiding an out-of-range commit when large temporary pools approach their capacity
• add a coarse Vulkan acceleration-structure build memory barrier so upload/copy writes and previous acceleration-structure build writes are visible to subsequent BLAS/TLAS builds; this is intentionally temporary until the common/renderer-level synchronization model records those implicit command accesses explicitly
• wire the swapchain acquire semaphore into the next queue submission instead of leaving it signaled and unwaited
• use acquire semaphores per frame slot, guarded by the queue timeline fence before reuse
• use present semaphores per swapchain image, so a binary present semaphore is not reused while presentation may still own it
• select a supported Vulkan swapchain composite-alpha mode and preserve destination alpha in the renderer compositing passes
• fix renderer debug-UI command-buffer sizing and use the correct DrawTextShaderParameters push-constant size
• simplify CPU timeline-fence waiting so LastCompletedFenceValue is updated after a successful vkWaitSemaphores

Validation status:

• classic Khronos validation and Best Practices remain enabled by --gpu-debug
• GPU-assisted validation remains optional through the existing GPU-validation option
• synchronization validation is temporarily disabled: with Vulkan SDK/VVL 1.4.357, its submit-time validation path intermittently causes VK_ERROR_DEVICE_LOST in the Renderer without reporting a useful SYNC-HAZARD-*; base validation, Best Practices, and SyncVal with submit-time validation disabled do not reproduce the failure
• this does not mean the synchronization model is considered fully validated; SyncVal should be revisited separately with a newer/fixed VVL or a targeted reproducer

Still intentionally deferred:

• swapchain SUBOPTIMAL / OUT_OF_DATE handling
• resize/fullscreen cleanup
• timestamp implementation
• memory/performance warnings
• the broader renderer/global barrier-model redesign
• re-enabling and re-validating synchronization validation

Do not consider the PR ready to merge until the current head has had a final local smoke test. Do not merge without explicit approval.