Add malicious PR security review workflow

[paullizer]

Summary

• Adds a malicious PR/file security review prompt for adversarial review of PRs, branch diffs, commit ranges, and explicit files.
• Adds a GitHub Actions workflow that runs the static checker on PRs into Development and via workflow_dispatch.
• Adds the static checker and functional coverage for dependency policy, hidden Unicode, suspicious egress markers, workflow/prompt wiring, and the version bump.

Validation

• python -m py_compile scripts/check_malicious_pr_security_review.py
• python functional_tests/test_malicious_pr_security_review_checker.py (4/4 passed)
• git -c core.whitespace=blank-at-eol,blank-at-eof,space-before-tab,cr-at-eol diff --cached --check

Issue

No associated GitHub issue was provided.