feat: add import resolution with Xenia-style thunk stubs (M8)

- resolve_imports() rewrites PE import records in-place:
  - Variable slots: 0xD000BEEF | (ordinal & 0xFFF) << 16
  - Thunk stubs: li r3, 0 / li r4, <ordinal> / mtspr CTR, r11 / bctr
- New -r/--resolve-imports flag on the extract command
- Without the flag, extraction is unchanged (byte-for-byte identical)

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

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "xex2tractor"
-version = "0.7.0"
+version = "0.8.0"
 edition = "2024"
 description = "A tool for extracting and inspecting Xbox 360 XEX2 executable files"
 license = "MIT"