Add a test setting that runs DLSS or FSR 3.1 before the bloom instead of after the tonemap.

Frame dumps show the upscaler reads the bloom composite's output, which the game has already exposed, bloomed and
tonemapped to 0..1. With dlss_prebloom = 1 it runs at the bloom chain's first pass on the scene's linear light. Without
upscaling its picture goes back into the light target. With upscaling the lens flares and the bloom composite are
drawn at the picture's size and that picture replaces the game's upscaler's output. Off by default; with it off
nothing changes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/architecture.md

@@ -219,6 +219,10 @@ keeps per-core data without locks and relies on that, so the host models it (`ru
   `taa` is DLSS or FSR at the scene's size with the game's SMAA. While DLSS or FSR runs (`dlaa`, any mode), the other
   values still choose the pass: in the native modes it smooths the upscaler's picture after the bloom, in the scaling
   modes it runs on the scene before the upscaler scales it.
+  DLSS and FSR 3.1 read the bloom composite's output, which the game has already exposed and tonemapped;
+  `NX2NAVI_DLSS_PREBLOOM=1` (a test, off by default) runs them at the bloom chain's first pass on the scene's linear
+  light instead, and draws the lens flares and the bloom composite after them at the picture's size (`vk_dlaa.c`,
+  "before the bloom").
 - HDR (`vk_hdr.c`): the game tonemaps its scene into a float target, upscales it, draws the HUD into a second float
   target and copies that into the 8-bit sRGB window texture it presents. With `NX2NAVI_HDR=1` the tonemap shader gets
   the function of `shaders/hdr_tonemap.frag` spliced in where its SDR curve clamps each channel, so the float picture