play_solo.bat: open gauges too (BT_DEV_GAUGES), matching join bats

Solo practice already started in-cockpit (BT_START_INSIDE) but didn't
open the MFD gauges window -- inconsistent with the join bats.  Add
BT_DEV_GAUGES=1 so single-player practice mirrors the pod experience.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

players/play_solo.bat

@@ -5,6 +5,7 @@ cd /d %~dp0
 if not exist "build\Release\btl4.exe" goto badpath
 if not exist "content\OPERATOR.EGG" goto badpath
 set BT_START_INSIDE=1
+set BT_DEV_GAUGES=1
 set BT_LOG=join.log
 cd content
 ..\build\Release\btl4.exe -egg ARENA1.EGG

tools/btoperator.py

@@ -826,7 +826,8 @@ class Operator(QMainWindow):
                 "operator).\n"
                 "rem Edit the -egg below for other maps "
                 "(ARENA2/DBASE/FOGDAY/...).\n",
-                "set BT_START_INSIDE=1\nset BT_LOG=join.log\n",
+                "set BT_START_INSIDE=1\nset BT_DEV_GAUGES=1\n"
+                "set BT_LOG=join.log\n",
                 "..\\build\\Release\\btl4.exe -egg ARENA1.EGG\n",
                 "echo.\necho The game has exited.  If it closed unexpectedly,\n"
                 "echo send the operator content\\join.log.\npause\n"))