chore: import humanlayer commands/agents updates

[jeffh]

Summary

• Re-imported all humanlayer commands and agents from the source repository
• Removed all humanlayer thoughts sync references from 12 command files
• Replaced scripts/spec_metadata.sh and hack/create_worktree.sh references with existing skills (spec-metadata and create-worktree)

Changes

• 18 files modified across commands and the import-humanlayer command itself
• Sync removal ensures commands work independently without the humanlayer CLI thoughts sync functionality
• Script-to-skill conversions use the existing skills in humanlayer/skills/