fix: run john stress in parallel per GPU, fix chromium fullscreen, filter BMC virtual disks

- bee-john-gpu-stress: spawn one john process per OpenCL device in parallel
  so all GPUs are stressed simultaneously instead of only device 1
- bee-openbox-session: --start-fullscreen → --start-maximized to fix blank
  white page on first render in fbdev environment
- storage collector: skip Virtual HDisk* devices reported by BMC/iDRAC

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

iso/overlay/usr/local/bin/bee-john-gpu-stress

@@ -190,4 +190,13 @@ CHOSEN_FORMAT=$(choose_format) || {
 }
 
 echo "format=${CHOSEN_FORMAT}"
-exec ./john --test="${SECONDS}" --format="${CHOSEN_FORMAT}" --devices="${JOHN_DEVICES}"
+PIDS=""
+for opencl_id in $(echo "${JOHN_DEVICES}" | tr ',' ' '); do
+    ./john --test="${SECONDS}" --format="${CHOSEN_FORMAT}" --devices="${opencl_id}" &
+    PIDS="${PIDS} $!"
+done
+FAIL=0
+for pid in ${PIDS}; do
+    wait "${pid}" || FAIL=$((FAIL+1))
+done
+[ "${FAIL}" -eq 0 ] || { echo "john: ${FAIL} device(s) failed" >&2; exit 1; }

iso/overlay/usr/local/bin/bee-openbox-session

@@ -24,7 +24,7 @@ chromium \
     --no-first-run \
     --disable-session-crashed-bubble \
     --disable-features=TranslateUI \
-    --start-fullscreen \
+    --start-maximized \
     http://localhost/ &
 
 exec openbox