feat: NVIDIA fix only for RTX 20 series or newer, with the VRAM booster's chwd legacy check (vram_nvidia_legacy_id)

TODO-nvidia.md

@@ -55,11 +55,14 @@ Today the fix runs unconditionally inside `gaming_enable`/`gaming_disable`.
 - [ ] README rows/screenshot rule (a release that adds a menu row retakes `assets/screenshot-menu.png`), TECHNICAL.md,
       CHANGELOG, `tests/nvidia-test.sh` (status/enable/disable through the component), VM menu test in
       steamify-cachyos-dev (`share/vmtest/menu`, TESTPLAN.md row).
-- [ ] What "compatible" means: see the research below. The parameters themselves apply to any card whose driver
-      provides `nvidia_drm` (what `nvidia_present` tests); whether gamescope works on a card is a separate question.
+- [x] What "compatible" means (decided 2026-10-01): RTX 20 series or newer, the same check as the VRAM booster
+      (`vram_nvidia_legacy_id`: a card on chwd's legacy lists `/var/lib/chwd/ids/nvidia-*.ids` is older; without the
+      lists every card counts). `nvidia_present` = such a card + `nvidia_drm` available; the toggle's `nvidia_available`
+      is the same function. Older cards (GTX 10/9 series) are left alone: no promise they work with gamescope.
 
 ## Older cards and other research
-The user hopes the fix also works for GPUs older than RTX 2000. Full notes with sources: **`NVIDIA-RESEARCH.md`**.
+Decision 2026-10-01: support RTX 20 series or newer only, with the VRAM booster's check (done in `lib/nvidia.sh`).
+The user had hoped older GPUs would work too; not promised. Full notes with sources: **`NVIDIA-RESEARCH.md`**.
 Short version: open kernel modules need Turing+, Maxwell/Pascal/Volta need the proprietary driver (580 legacy branch);
 `nvidia-drm.modeset/fbdev` exist in both, so the fix applies to any card with `nvidia_drm`, but nothing found says gamescope
 works better or worse there (a GTX 1050 Ti has a known gamescope>3.16.16 start problem on HDMI, not ours). Cannot be promised: