Close-out: clean-slate doc fix, 150% scaling landed, #679 queued (#631/#679)

Full RDP clean slate requires killing session processes AND stopping
user@UID (sessions live in the system sesman cgroup - reconnect into a
survivor never restarts the user manager). 150% HiDPI + core cursors
persisted both accounts. Display-performance work (16K compressed-PDU
drops, staged 1MB send buffer, EGFX-at-24bpp retest) captured as #679.

Details: https://projects.knownelement.com/issues/679

12-fix-rdp-bigres.sh

@@ -115,12 +115,14 @@ echo "EGFX disabled (drdynvc=false) — clients now negotiate classic codecs."
 #   (iPad backgrounding Jump) are detected; reconnects then RESUME the
 #   existing session instead of spawning duplicates.
 # - THE CLEAN SLATE, when a login black-screens and nothing else works:
-#   the systemd --user manager accumulates poisoned state across session
-#   generations (stale DISPLAY env, wedged dbus name waits — plasma units
-#   are Type=dbus and hang "activating" at ~0% CPU). Recycle it:
-#       systemctl stop user@<uid>
-#   then reconnect (fresh manager = clean login at ANY resolution).
-#   pkill of kwin/plasmashell/Xorg alone does NOT reach this layer.
+#   TWO layers must both go, or reconnects black-screen:
+#     a) the RDP sessions themselves (system cgroup! user@UID stop does
+#        NOT reach them): stop xrdp; pkill xrdp-sesexec + the xrdp Xorgs
+#     b) the systemd --user manager, which accumulates poisoned state
+#        (stale DISPLAY env, wedged dbus name waits; plasma units are
+#        Type=dbus and hang "activating" at ~0% CPU): systemctl stop user@<uid>
+#   Reconnecting into a SURVIVING session does not restart the user
+#   manager -> black screen. Kill both, then start xrdp and reconnect.
 ###############################################################################
 
 grep -q '^DisconnectedTimeLimit=0' /etc/xrdp/sesman.ini || sed -i 's/^DisconnectedTimeLimit=.*/DisconnectedTimeLimit=0/' /etc/xrdp/sesman.ini