rpi: drop to interactive shell on boot failure, add initcall_debug

Instead of returning 1 (which triggers kernel panic via set -e before
emergency_shell runs), exec an interactive shell on /dev/console so
the user can run dmesg and debug interactively. Add initcall_debug
and loglevel=7 to cmdline.txt to show every driver probe during boot.
Also dump last 60 lines of dmesg before dropping to shell.

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

build/scripts/create-rpi-image.sh

@@ -173,7 +173,7 @@ CFGTXT
 
     # cmdline.txt — kernel command line
     # Note: must be a single line
-    echo "console=serial0,115200 console=tty1 kubesolo.data=LABEL=KSOLODATA" > "$MNT/cmdline.txt"
+    echo "console=serial0,115200 console=tty1 kubesolo.data=LABEL=KSOLODATA initcall_debug loglevel=7" > "$MNT/cmdline.txt"
 
     # Copy kernel as kernel8.img (RPi 3/4/5 ARM64 convention)
     cp "$KERNEL" "$MNT/kernel8.img"