fix: disk image build, piCore64 URL, license

- Add kpartx for reliable loop partition mapping in Docker containers
- Fix piCore64 download URL (changed from .img.gz to .zip format)
- Fix piCore64 boot partition mount (initramfs on p1, not p2)
- Fix tar --wildcards for RPi firmware extraction
- Add MIT license (same as KubeSolo)
- Add kpartx and unzip to Docker builder image

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

build/scripts/extract-core.sh

@@ -29,23 +29,40 @@ if [ "$EXTRACT_ARCH" = "arm64" ]; then
 
     echo "==> Extracting piCore64 image: $PICORE_IMG"
 
-    # Decompress .img.gz to raw image
+    # Decompress to raw image (.img.gz or .zip)
     PICORE_RAW="$CACHE_DIR/piCore-${PICORE_VERSION}.img"
     if [ ! -f "$PICORE_RAW" ]; then
         echo "    Decompressing..."
-        gunzip -k "$PICORE_IMG" 2>/dev/null || \
-            zcat "$PICORE_IMG" > "$PICORE_RAW"
+        case "$PICORE_IMG" in
+            *.zip)
+                unzip -o -j "$PICORE_IMG" '*.img' -d "$CACHE_DIR" 2>/dev/null || \
+                    unzip -o "$PICORE_IMG" -d "$CACHE_DIR"
+                # Find the extracted .img file
+                EXTRACTED_IMG=$(find "$CACHE_DIR" -maxdepth 1 -name '*.img' -newer "$PICORE_IMG" | head -1)
+                if [ -n "$EXTRACTED_IMG" ] && [ "$EXTRACTED_IMG" != "$PICORE_RAW" ]; then
+                    mv "$EXTRACTED_IMG" "$PICORE_RAW"
+                fi
+                ;;
+            *.img.gz)
+                gunzip -k "$PICORE_IMG" 2>/dev/null || \
+                    zcat "$PICORE_IMG" > "$PICORE_RAW"
+                ;;
+            *)
+                echo "ERROR: Unknown piCore image format: $PICORE_IMG"
+                exit 1
+                ;;
+        esac
     fi
 
-    # Mount the piCore rootfs partition (partition 2 in the SD image)
-    # Use losetup to find the partition offset
+    # Mount the piCore boot partition (partition 1) to find kernel/initramfs
+    # piCore layout: p1=boot (FAT32, has kernel+initramfs), p2=rootfs (ext4, has tce/)
     IMG_MNT=$(mktemp -d)
-    echo "    Mounting piCore rootfs partition..."
+    echo "    Mounting piCore boot partition..."
 
-    # Get partition 2 offset (piCore layout: boot=p1, rootfs=p2)
-    OFFSET=$(fdisk -l "$PICORE_RAW" 2>/dev/null | awk '/^.*img2/{print $2}')
+    # Get partition 1 offset (boot/FAT partition with kernel+initramfs)
+    OFFSET=$(fdisk -l "$PICORE_RAW" 2>/dev/null | awk '/^.*img1/{print $2}')
     if [ -z "$OFFSET" ]; then
-        # Fallback: try sfdisk
+        # Fallback: try sfdisk (first partition)
         OFFSET=$(sfdisk -d "$PICORE_RAW" 2>/dev/null | awk -F'[=,]' '/start=/{print $2; exit}' | tr -d ' ')
     fi
     if [ -z "$OFFSET" ]; then
@@ -56,13 +73,13 @@ if [ "$EXTRACT_ARCH" = "arm64" ]; then
 
     BYTE_OFFSET=$((OFFSET * 512))
     mount -o loop,ro,offset="$BYTE_OFFSET" "$PICORE_RAW" "$IMG_MNT" || {
-        echo "ERROR: Failed to mount piCore rootfs (need root for losetup)"
+        echo "ERROR: Failed to mount piCore boot partition (need root for losetup)"
         exit 1
     }
 
-    # Find initramfs in the piCore rootfs
+    # Find initramfs in the piCore boot partition
     COREGZ=""
-    for f in "$IMG_MNT"/boot/corepure64.gz "$IMG_MNT"/boot/core.gz "$IMG_MNT"/*.gz; do
+    for f in "$IMG_MNT"/rootfs-piCore64*.gz "$IMG_MNT"/boot/corepure64.gz "$IMG_MNT"/boot/core.gz "$IMG_MNT"/corepure64.gz "$IMG_MNT"/core.gz; do
         [ -f "$f" ] && COREGZ="$f" && break
     done