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 quiet" > "$MNT/cmdline.txt"
+    echo "console=serial0,115200 console=tty1 kubesolo.data=LABEL=KSOLODATA initcall_debug loglevel=7" > "$MNT/cmdline.txt"
 
     # Copy kernel as kernel8.img (RPi 3/4/5 ARM64 convention)
     cp "$KERNEL" "$MNT/kernel8.img"

init/lib/20-persistent-mount.sh

@@ -58,12 +58,46 @@ esac
 
 if [ ! -b "$KUBESOLO_DATA_DEV" ]; then
     log_err "Data device $KUBESOLO_DATA_DEV not found after ${WAIT_SECS}s"
-    # Show available block devices for debugging
-    log_err "Available block devices:"
-    ls -la /dev/mmc* /dev/sd* /dev/vd* 2>/dev/null | while read -r line; do
+    # Comprehensive diagnostics for block device failure
+    log_err "=== Block device diagnostics ==="
+    log_err "--- /dev block devices ---"
+    ls -la /dev/mmc* /dev/sd* /dev/vd* /dev/nvme* 2>/dev/null | while read -r line; do
         log_err "  $line"
     done
-    return 1
+    log_err "--- /sys/class/block (kernel registered) ---"
+    ls /sys/class/block/ 2>/dev/null | while read -r line; do
+        log_err "  $line"
+    done
+    log_err "--- dmesg: MMC/SDHCI/emmc ---"
+    dmesg 2>/dev/null | grep -i -e mmc -e sdhci -e emmc | while read -r line; do
+        log_err "  $line"
+    done
+    log_err "--- dmesg: regulator ---"
+    dmesg 2>/dev/null | grep -i regulator | while read -r line; do
+        log_err "  $line"
+    done
+    log_err "--- dmesg: firmware/mailbox ---"
+    dmesg 2>/dev/null | grep -i -e 'raspberrypi' -e 'mailbox' -e 'firmware' | while read -r line; do
+        log_err "  $line"
+    done
+    log_err "--- dmesg: errors ---"
+    dmesg 2>/dev/null | grep -i -e 'error' -e 'fail' -e 'unable' | while read -r line; do
+        log_err "  $line"
+    done
+    log_err "--- Full dmesg (last 60 lines) ---"
+    dmesg 2>/dev/null | tail -60 | while read -r line; do
+        log_err "  $line"
+    done
+    log_err "=== End diagnostics ==="
+    log_err ""
+    log_err "Dropping to debug shell in 10 seconds..."
+    log_err "Run 'dmesg' to see full kernel log."
+    log_err "Run 'ls /sys/class/block/' to check block devices."
+    log_err ""
+    sleep 10
+    # Drop to interactive shell instead of returning failure
+    # (returning 1 with set -e causes kernel panic before emergency_shell)
+    exec /bin/sh </dev/console >/dev/console 2>&1
 fi
 
 # Mount data partition (format on first boot if unformatted)