Make the console (kid) account name configurable

Autostart reads CONSOLE_KID_USER from /etc/bc250-console.conf
(default: kid), so renaming the account is a pure on-box operation —
documented in OPERATIONS.md.

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

files/console/usr/bin/bc250-steam-bpm-autostart

@@ -7,7 +7,10 @@
 # status-clobbering bug, producing a zenity "ERROR: code=0; This is
 # strange..." popup at login whenever Steam lingered from a previous
 # session. We do the same quit-first dance robustly instead.
-[ "$(id -un)" = "kid" ] || exit 0
+# Which account gets the console treatment; override the default after a
+# rename with: echo 'CONSOLE_KID_USER=newname' > /etc/bc250-console.conf
+[ -r /etc/bc250-console.conf ] && . /etc/bc250-console.conf
+[ "$(id -un)" = "${CONSOLE_KID_USER:-kid}" ] || exit 0
 
 if pgrep -u "$(id -u)" -f 'steam\.sh|ubuntu12_32/steam' >/dev/null 2>&1; then
     /usr/bin/steam +quit >/dev/null 2>&1 || true

files/console/usr/share/doc/bc250-console/OPERATIONS.md

@@ -53,6 +53,22 @@ cat /sys/class/drm/card*/device/pp_dpm_sclk   # GPU clock scaling
 df -h /                                       # disk space
 ```
 
+## Renaming the kid's account (optional)
+
+With the kid fully logged out (`sudo loginctl terminate-user kid`):
+
+```bash
+sudo usermod  -l NEWNAME kid
+sudo groupmod -n NEWNAME kid
+sudo usermod  -d /home/NEWNAME -m NEWNAME
+sudo chfn -f "Display Name" NEWNAME
+sudo passwd NEWNAME
+echo 'CONSOLE_KID_USER=NEWNAME' | sudo tee /etc/bc250-console.conf
+```
+
+Steam data and apps live in the home directory and move with it. The last
+line tells the Big Picture autostart which account is the console account.
+
 ## Tuning the GPU (optional, after thermal testing)
 
 The GPU governor's curve lives at