[codex] Add public readiness checks

[amitkot]

Summary

• Scrub current HEAD of project-specific public-readiness references and local machine paths.
• Add local public-readiness and repo hygiene checks wired through pre-commit and just audit-public.
• Add GitHub Actions coverage that installs gitleaks and runs pre-commit on pushes and PRs.

Validation

• just audit-public
• pre-commit run --all-files
• bash -n tools/audit_public.sh
• bash -n tools/pre_commit_checks.sh
• YAML parse check for .pre-commit-config.yaml and .github/workflows/pre-commit.yml
• git diff --check

Note: local gitleaks is not installed, so the local audit printed the install/run guidance; CI installs gitleaks before running pre-commit.