Add the optional Forward+ desktop HQ build

Package a Forward+ preset with volumetric fog, SDFGI and a volumetric flashlight
for a separate Linux/Windows Desktop HQ zip. Gate the effects on a real
RenderingDevice, tune LATE fog, and adapt local light falloff for Godot 4.7.
Record the Compatibility/Forward+ A/B captures and metrics, add the artifact to
the build/publish scripts, and keep the default Compatibility/Web path
unchanged. Headless 231/231, Python 87/87; exported HQ binary boots with Vulkan.

docs/screens/realism/2026-11-01-forward-plus/report.md

@@ -0,0 +1,42 @@
+# Realism report: `docs/screens/realism/2026-11-01-forward-plus`
+
+| set | shot | target | gap ↓ | edges | detail | contrast | overall | lighting | materials | texture | backdrop |
+| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
+| baseline | entrance_late | hollywood_entrance_rain_night | 1.568 | 21.3 | 9.55 | 68.03 | - | - | - | - | - |
+| baseline | street_late | boulevard_skyline_dusk | 0.247 | 10.57 | 6.21 | 26.84 | - | - | - | - | - |
+| candidate | entrance_late | hollywood_entrance_rain_night | 1.187 | 19.31 | 8.37 | 55.27 | - | - | - | - | - |
+| candidate | street_late | boulevard_skyline_dusk | 0.258 | 11.4 | 6.21 | 27.58 | - | - | - | - | - |
+
+Mean scores per set (all captured shots):
+
+| set | shots | gap ↓ | overall | lighting | materials | texture_detail | backdrop | characters |
+| --- | --- | --- | --- | --- | --- | --- | --- | --- |
+| baseline | 2 | 0.907 | - | - | - | - | - | - |
+| candidate | 2 | 0.723 | - | - | - | - | - | - |
+
+
+## Desktop HQ A/B
+
+`baseline` is the normal GL Compatibility build; `candidate` is the same
+staging with `packaging/desktop_hq/override.cfg` beside the project (Forward+,
+SDFGI and volumetric fog). Both use `--stages=late --flashlight`.
+
+The entrance metric gap improved **1.568 → 1.187** and the two-shot mean
+**0.907 → 0.723**. The flashlight now lights the door instead of disappearing
+into the dark, while the LATE volumetric density (0.020) leaves the brick
+facade readable instead of washing it out. `street_late` is nearly unchanged
+(0.247 → 0.258), which is expected because the fog is tuned around the
+entrance.
+
+Capture command:
+
+```bash
+cp packaging/desktop_hq/override.cfg ./override.cfg
+xvfb-run -a godot --path . --script res://src/test/capture_realism.gd -- \
+  --stages=late --flashlight \
+  --out=res://docs/screens/realism/2026-11-01-forward-plus/candidate
+rm override.cfg
+```
+
+The vision judge could not run because `OPENROUTER_API_KEY` is invalid; the
+retry is recorded in `TODO.md`.