Add runnable examples and OSS readiness checks

[cigan1]

Summary

• add README and package metadata links for runnable examples, tools, and pricing
• add OSS readiness docs, issue/PR templates, CODEOWNERS, Dependabot, and compliance checks
• harden GitHub Actions permissions, concurrency, package build validation, and PyPI publish action pinning

Validation

• ruff check .
• mypy
• pytest
• python -m build
• README audit: go
• license audit: go
• workflow audit: go