docs: record the Linux hardware sign-off

docs/validation.md

@@ -9,7 +9,7 @@ pass/fail results.
 | Where | Script | Status |
 | --- | --- | --- |
 | Linux, headless rig (Wayland portal + Xwayland) | `scripts/validate/linux-rig.sh` | All 9 scenarios pass on devbox (Intel UHD 770, VA-API) |
-| Linux, real session (CachyOS, Hyprland, RX 9070 XT, 1440p60) | `scripts/validate/linux-hardware.sh` | 2026-10-08: H.264, HEVC and AV1 usable; restore token works |
+| Linux, real session (CachyOS, Hyprland, RX 9070 XT, 1440p60) | `scripts/validate/linux-hardware.sh` | Passed 2026-10-08 (run 4, dc9cbd6) |
 | Windows (Game Capture, NVENC/AMF/QSV) | `scripts/validate/windows.ps1` | Not run yet; script untested |
 
 ## Probe commands
@@ -94,6 +94,14 @@ CachyOS 7.2.9, Hyprland, RX 9070 XT, 1440p60, OBS 32.0.4:
 - A portrait monitor (Hyprland transform 3) is captured as 1440x2560 and
   pillarboxed in the 2560x1440 canvas.
 
+### Fourth hardware run: pass (2026-10-08, dc9cbd6)
+
+After restarting xdg-desktop-portal-hyprland, every step passed: H.264, HEVC
+and AV1 through VA-API at 1440p60, monitor and window capture with motion,
+keyframe-aligned segments that remux across boundaries, and a restored
+selection that skipped the picker. Closing a window was again not detected
+(informational, see findings).
+
 ## Windows
 
 Run `scripts/validate/windows.ps1 -GameWindow "<title>:<class>:<exe>"` with a