feat: add failure replay proof surface

[stevenchouai]

Summary

• Adds a static examples/reports/failure-replay.html proof page showing how a bad agent trace changes the next autonomy decision.
• Links the replay from the root README and reports index.
• Extends static viewer tests to verify key content, local links, and public-safety constraints.

Test plan

• python -m pytest
• git diff --check
• Independent reviewer pass: no security concerns or logic errors after privacy/link fixes.