Sync workflows lack validation of synced skill files

[StencilwashCoder]

The sync-anthropic-official.yml workflow syncs the official Anthropic skills repo, but there's no validation that synced files are actually valid Claude Code skills. A broken or malformed skill file from upstream could be auto-committed to this repo without any checks.

The workflow should:

1. Validate that each synced file has required skill metadata (name, description, version)
2. Check that referenced scripts/files actually exist
3. Run a basic syntax check on any code files
4. Fail the workflow if validation doesn't pass, preventing broken files from entering the repo

Currently the workflow just copies files blindly, which could introduce broken or even malicious skill definitions from third-party repos.