Phase 0: browser X11-overlay inventory + mpv reference cell + tooling installs

Source-level verdict: no browser in the matrix has a code path
to hand NV12 to the X server for plane scanout. Chromium ozone-x11
wires StubOverlayManager (ozone_platform_x11.cc:262); Brave 147 +
chromium-fourier 149 inherit unchanged. Firefox WindowSurfaceX11
is RGB-only. The campaign's load-bearing hypothesis is structurally
weakened — what the X11 cells will measure for browsers is
KWin's per-frame RGB-recomposite cost, not the original
"force-GL-composite of NV12" framing. mpv --vo=xv becomes the
matrix's only direct test of the operator-supplied mechanism.

Matrix updated: 12 cells -> 16 cells (+8 mpv VO sub-points).
revert.log entries 1-5 capture all package + per-user state
mutations from this turn (measurement tools, openbox, XFCE +
xfwm4-no-comp pre-seed, firefox + AUR xtrace, XFCE rotation
+ touchscreen mapping); single SSH-driveable revert chain
returns ohm to its pre-campaign 1169-package state.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

phase0_evidence/x11_inventory_2026-05-03/pacman.install.log

@@ -0,0 +1,47 @@
+resolving dependencies...
+looking for conflicting packages...
+
+Packages (11) libadwaita-1:1.9.0-1  libdex-1.1.0-1  libpanel-1.10.4-1  startup-notification-0.12-9  openbox-3.6.1-14  sysprof-50.0-2  xorg-xev-1.2.6-2  xorg-xinput-1.6.4-2  xorg-xkill-1.0.7-1  xorg-xrandr-1.5.4-1  xorg-xwininfo-1.1.6-2
+
+Total Download Size:    2.31 MiB
+Total Installed Size:  16.01 MiB
+
+:: Proceed with installation? [Y/n] 
+:: Retrieving packages...
+ sysprof-50.0-2-aarch64 downloading...
+ libadwaita-1:1.9.0-1-aarch64 downloading...
+ openbox-3.6.1-14-aarch64 downloading...
+ libpanel-1.10.4-1-aarch64 downloading...
+ libdex-1.1.0-1-aarch64 downloading...
+ xorg-xrandr-1.5.4-1-aarch64 downloading...
+ xorg-xinput-1.6.4-2-aarch64 downloading...
+ xorg-xwininfo-1.1.6-2-aarch64 downloading...
+ startup-notification-0.12-9-aarch64 downloading...
+ xorg-xev-1.2.6-2-aarch64 downloading...
+ xorg-xkill-1.0.7-1-aarch64 downloading...
+checking keyring...
+checking package integrity...
+loading package files...
+checking for file conflicts...
+:: Processing package changes...
+installing xorg-xrandr...
+installing xorg-xev...
+installing xorg-xinput...
+installing xorg-xwininfo...
+installing xorg-xkill...
+installing libadwaita...
+installing libdex...
+installing libpanel...
+installing sysprof...
+installing startup-notification...
+installing openbox...
+Optional dependencies for openbox
+    python-pyxdg: for the openbox-xdg-autostart script
+:: Running post-transaction hooks...
+(1/7) Reloading system manager configuration...
+(2/7) Updating the MIME type database...
+(3/7) Arming ConditionNeedsUpdate...
+(4/7) Refreshing PackageKit...
+(5/7) Reloading system bus configuration...
+(6/7) Updating icon theme caches...
+(7/7) Updating the desktop file MIME type cache...