Add polished examples pack

[httpdss]

Summary

• Replace the old singular example/ directory with a documented examples/ pack.
• Add five runnable examples: Python CLI, FastAPI service, Terraform module, GitHub Actions CI baseline, and AI agent/MCP scaffold.
• Add per-example READMEs, a top-level examples index, and update README/docs/docker-compose references away from the removed example/ path.

Verification

• Ad-hoc /tmp/hermes-verify-structkit-examples-* script:
  • checked local markdown links for changed docs/example files
  • ran structkit validate for all five example .struct.yaml files
  • generated all five examples into a temporary directory and verified expected files
  • checked for stale example/structure.yaml references
• pre-commit run --all-files
• git diff --cached --check

Notes

• A focused pytest command was attempted, but local collection is blocked by a missing github Python module in this environment (ModuleNotFoundError: No module named 'github').

Closes #154