Add ipctool backup format support to defib restore

[widgetii]

Summary

defib restore now accepts ipctool backup files directly — no extraction step needed.

# One command to restore from ipctool backup:
defib restore -c hi3516av200 -i backup.bin \
  --uboot u-boot.bin -p /dev/ttyUSB0 --power-cycle

How it works

• Auto-detects ipctool format from ---\n YAML prefix
• Extracts mtdparts from embedded YAML (no --mtdparts needed)
• Extracts partition data blocks (YAML + null + [4-byte len + data]*)
• UBI partitions auto-detected from UBIFS magic and written via ubi write

Also fixes

• mtdparts parser for -(name) fill-remainder syntax (last partition)

Test result

Full round-trip on hi3516av200 (128MB SPI NAND):

1. ipctool backup on live camera → test-backup.bin (110MB, 7 partitions)
2. defib restore -i test-backup.bin → all 7 partitions written
3. Cold boot → all 6 UBIFS volumes mount, vendor firmware runs

UBIFS: mounted "rootfs"    ✓
UBIFS: mounted "data"      ✓
UBIFS: mounted "upgradefs" ✓
UBIFS: mounted "appfs"     ✓
UBIFS: mounted "exdata"    ✓
(none) login:              ✓
Sony IMX385 → OK           ✓

Test plan

• 326 tests pass, lint + mypy clean
• Restore from ipctool backup file on real hardware
• All UBIFS volumes mount after cold boot
• Vendor firmware fully operational

🤖 Generated with Claude Code