midi-autoconnect: rule 4 costs one aconnect per tick while healthy

Bash regex instead of a grep fork, and the driver's own virtual port as proof
of service so systemctl is only asked when the raw board is present without
it.

tools/midi-autoconnect.sh

@@ -199,17 +199,22 @@ DRIVER_TRIES=0
 DRIVER_LAST=0
 DRIVER_STATE=""
 
-raw_lcxl3_present() {
-    aconnect -l 2>/dev/null | grep -Eq "^client [0-9]+: 'LCXL3[^']*' \[type=kernel"
-}
-
 ensure_surface_driver() {
-    local now
-    if ! raw_lcxl3_present; then
+    # One aconnect per tick and no systemctl while healthy: this loop runs every
+    # 2 s for the whole session, and forks are its whole cost. The driver's own
+    # virtual port is the proof it is serving; only when that port is missing
+    # while the raw board is present do we ask systemd.
+    local now ac
+    local raw_re="client [0-9]+: 'LCXL3[^']*' \[type=kernel"
+    ac="$(aconnect -l 2>/dev/null)"
+    if ! [[ "$ac" =~ $raw_re ]]; then
         DRIVER_TRIES=0
         DRIVER_STATE="absent"
         return 0
     fi
+    if [[ "$ac" == *"'ParVagues LCXL3"* ]] && [ "$DRIVER_STATE" = "up" ]; then
+        return 0                                  # steady state: zero extra forks
+    fi
     if systemctl --user is-active --quiet "$DRIVER_UNIT"; then
         if [ "$DRIVER_STATE" != "up" ]; then
             echo "midi-autoconnect: LCXL3 present, lcxl3-driver is up"