[mitch030504]

Changes

• Add ABadAvatar 1.3 Beta as a separate exploit option
• Keep the original Shutterbug2000 ABadAvatar release available
• Pin ABadAvatar 1.3 Beta to the exact avatar-v1.3-beta release
• Pin the published SHA-256 for the release asset
• Validate both BadUpdatePayload and Content archive roots
• Add a regression test for repository, tag, asset, digest, and archive layout
• Add prerelease/internet/Kinect warnings to the README
• Credit Bibarub for the ABadAvatar 1.3 Beta build
• Bump BadBuilderLinux to 2.2.0

Validation

• Release asset SHA-256 manually verified
• Archive contents manually inspected
• 43/43 normal tests pass
• 43/43 BADBUILDER_LIVE_SMOKE tests pass
• linux-x64 self-contained publish succeeds
• win-x64 self-contained publish succeeds
• git diff --check passes