perf(rendering): preserve alpha order with bindless particles

Carry each billboard particle's resident texture handle in the instance ABI so stable retail alpha ordering can batch mixed textures without rebinding and redrawing each short texture run. Keep DAT blend transitions as the only billboard draw boundary.

The connected 0xC95B stress scene improved from 6 FPS / 171 ms to about 153 FPS / 6.6 ms at the same roughly 21,000 visible entities. Release build succeeds and all 5,916 tests pass with five intentional skips.

Co-authored-by: OpenAI Codex <codex@openai.com>

docs/architecture/worldbuilder-inventory.md

@@ -138,6 +138,10 @@ acdream-owned runtime seam above the extracted mesh pipeline. During the main
 world frame, `WbDrawDispatcher` and `ParticleRenderer` submit transparent
 GfxObj subsets and scene particles into one stable far-to-near stream keyed by
 the transformed DAT `SortCenter`; only adjacent compatible entries may batch.
+Billboard particle textures are resident bindless `sampler2DArray` handles in
+the per-instance vertex ABI, so different textures preserve that sorted order
+inside one instanced draw; only a DAT blend-mode boundary splits the run. This
+keeps dense particle fields from becoming one GL draw per alternating texture.
 `RetailPViewRenderer` drains the landscape scope before the optional depth
 clear, and `GameWindow` drains the final scope before private viewports/UI.
 Sky and sealed off-screen render targets remain independent. No DAT reader,