[User Story] Remove alloy-sysext-build from ghost repository

[noahwhite]

Description

Clean up the ghost repository by removing the alloy-sysext-build directory after successful migration and verification of the new automated build pipeline.

Acceptance Criteria

• Verify new repository is fully functional
• Verify CI/CD pipeline has run successfully at least once
• Verify R2 bucket contains the expected artifacts from automated build
• Delete /workspace/alloy-sysext-build directory from ghost repo
• Update ghost repository README if it references this directory
• Commit changes and create PR with removal

Directory to Remove

• /workspace/alloy-sysext-build/

Pre-Cleanup Verification Checklist

• New alloy-sysext-build repo is public and accessible
• At least one successful build has completed
• Artifacts are available in R2 bucket
• Documentation is complete in new repo

Dependencies

This is the final cleanup task and depends on all previous user stories:

• GHO-32: Repository created
• GHO-33: Files migrated
• GHO-34: CI/CD implemented
• GHO-35: R2 integration working
• GHO-36: Documentation updated

[linear]

GHO-37