[codex] Add public fixture baselines

[hudsonaikins]

Summary

Adds committed fixture baselines for the public PermitGraph proof artifacts so demo scans can show both current findings and frozen baseline keys for future diff scans.

Changes

• Extends tools/build_public_demo_artifacts.py to write deterministic finding-baseline.json files.
• Adds baselines for safe-agent, risky-ci-agent, and risky-mcp-agent.
• Updates README and docs to include baseline artifacts in the public proof path.
• Keeps baseline timestamps fixed for stable diffs.

Validation

• python3 tools/release_check.py
• 134 Python tests passed
• repository self-scan passed with Permit status: approved
• Python package build passed
• dashboard lint/build passed
• documentation site build passed
• worker bun run check
• worker bun test passed 6 tests

Notes

No infrastructure was deployed in this PR.